If the median of list B is exactly 4 higher than the median of list A

A = {10, 4, 7, 18}

B = {x, 10, 4, 7, 18, 25}

If the median of list B is exactly 4 higher than the median of list A, what is the value of x?

A. 12.5
B. 15
C. 18
D. 24
E. 25