If P(2, m) is the midpoint of the line joining Q(m, n) and R(n, -4), find the values of m and n.

A. m = 0, n = 4
B. m = 4, n = 0
C. m = 2, n = 2
D. m = -2, n = 4

Correct Answer: Option A

A. m = 0, n = 4