Does Mary's Question Contradict other passages in the NT?

In Luke 1:34 Mary asks the question. After the angel proclaims to Mary, "And behold, you will conceive in your womb and bear a son, and you shall call his name Jesus," Mary's reply is "How shall this be done, because I know not man?"(DR, NJB) or "since I am a virgin?"(NIV) In more bold translations the question is rendered "since I have no husband?"(RSV) or "since I know not a man?" (KJV). The latter translations make little contextual sense, when one considers that the evangelist told us a few verses earlier that the virgin is "espoused to a man whose name [is] Joseph, of the House of David." (v. 27) Although the meaning of this question is unclear many writers have felt free to give what they are sure is the definite explanation for this verse, represented here by St. Augustine, "She only asks about the manner-Because I know not man. This answer would have been to no purpose had she not made a vow to God to live always a virgin." St Gregory of Nissa writes, "She did not doubt the truth of what the angel said but she wished it might not happen to the prejudice of her vowed virginity." However, more modern commentators, such as those of the NJB have written, "The virgin Mary is only 'betrothed' (v. 27) and does not have conjugal relations (a semitic sense of 'know'). The seeming opposition of this and the promise of vv. 31-33 calls forth the explanation of v. 35. Nothing in the text suggests a vow of virginity."

1. If Mary made a previous vow of virginity, which I find unlikely, then how can this be recognized with her betrothal which was in place prior to the annunciation?

2. If Mary is simply asking who will impregnate her, then this seems like a silly question as she is already espoused to Joseph.

3. I think it's silly to suggest that Mary was ignorant of how babies come into the world.

Does Mary's question contradict Luke 1:27 and Matthew 1:18 (which uses the aorist participle mnesteutheises showing that Joseph and Mary were betrothed prior to the recorded events)?

Please help!

..................................
" Mary had not yet had sexual contact with a man, for Luke called her a virgin (parthenon; cf. 1:34) and noted that she was pledged to be married to . . . Joseph (cf. 2:5). In Jewish culture then a man and woman were betrothed or pledged to each other for a period of time before the actual consummation of their marriage. This betrothal was much stronger than an engagement period today, for the two were considered husband and wife except that they did not live together till after the wedding."

Walvoord, J. F., Zuck, R. B., & Dallas Theological Seminary. (1983-c1985). The Bible knowledge commentary : An exposition of the scriptures. Wheaton, IL: Victor Books."

....................................

"Mary's question to the angel (34) is puzzling. If she was engaged to be married to a descendant of David, as Joseph is explicitly described (27), why should she ask how this was going to happen and say I am a virgin (lit. 'I do not know a man' in the sense of having sexual relations with him)? Would not the child be the natural result of her impending marriage? Some have argued that Mary had taken a vow of virginity, but this would have been impossible for a Jewish girl engaged to be married. She may have taken the angel to be referring to an immediate conception which would have been out of the question before marriage. Whatever the explanation, the question enabled the angel to explain more fully that Mary's son would not be a merely human being, adopted by God as his Son (like David's son in 2 Sa. 7:12-14), but really and truly God's own Son whose birth would be brought about by the power of God's Spirit."
Carson, D., & Guthrie, D. (1997, c1994). New Bible Commentary : 21st century edition (electronic ed. of the 4th ed.) (Lk 1:26). Downers Grove: InterVarsity.
.......................................

"The resultant tracing of the ancestry through the mother is not usual, but Hillel is said to have traced for himself Davidic ancestry through his mother...The virginity of Mary functions, in parallel with Elizabeth's barrenness, as an obstacle to the production of the promised child. It is exalted neither as of value in itself (as commonly assumed in Catholic study) nor as a mark of spiritual humility. Her virginity is repeatedly stressed (twice here and in v 34) to underline the magnitude of the miracle (and cf. the similar function of vv 36, 37). In the present text the betrothal to Joseph serves to provide (legal) Davidic ancestry for the child. In Jewish tradition a girl was normally betrothed in the thirteenth year and for legal but not domestic purposes was from that point on considered to be married. Around a year later the girl was taken to the bridegroom's home for normal married life to begin. Sexual relations prior to this "taking home" would be considered a violation of marriage customs (cf. Str-B, 1:45-47; 2:393-98; Gaechter, Maria, 79-92).

Evans, C. (2002). Vol. 35A: Word Biblical Commentary : Luke 1:1-9:20. Word Biblical Commentary (Page 49). Dallas: Word, Incorporated.

"A traditional view, still held by a few recently, is that Mary understood the angel to be announcing an imminent pregnancy. The future tenses of 1:31, 35 could argue against such a near-term view, nevertheless a case can be made for it, because several terms, in 1:28-30 suggest a near fulfillment. Mary is addressed with the perfect tense in 1:28 as one who is in a "favored state." In the same verse she is told "the Lord is with you." Finally, in 1:30 she is told that she "has found grace" with God The exchange of tenses suggests a potential immediacy. So she takes the announcement not to be of a future birth in her marriage, but of an immediate birth. In addition, she may have concluded that Joseph came from too humble a background to be the source of such a child. So Mary asks her question." [Luke, Darrell Bock, Baker Publish.]