In a row of boys, if A is 10th from left and B is 9th from the right and interchange their positions, A becomes 15th from the left. How many boys are there in the row?

In a row of boys, if A is 10th from left and B is 9th from the right a

1.	In a row of boys, if A is 10th from left and B is 9th from the right and interchange their positions, A becomes 15th from the left. How many boys are there in the row?
A.	23
B.	27
C.	28
D.	31
Answer» B. 27