Geometry math question please help

In the parallelogram, the diagonals divide to halves. Therefore we have the equaetions:
2x = x + 2 and 4y - 8 = y + 10
2x = x + 2 |-2
x = 2
4y - 8 = y + 10 |+8
4y = y + 18 |-y
3y = 18 |:3
y = 6
AC = 2x + x + 2 = 3x + 2
substitute the value of x:
AC = 3(2) + 2 = 6 + 2 = 8
Answer: C. 8