In a row of students P was standing $$17^{th}$$ from the left end and $$23^{rd}$$ from the right end. If Q was standing exactly in the middle of the row, what was his position from the left end? (Assume students were facing the north.)

A

$$20^{th}$$

B

$$18^{th}$$

C

$$22^{nd}$$

D

$$19^{th}$$