The domain of f(x)=1/2x-3 is {-2, 4, 10, 15}. What is the range?

A. {-2, 1, 2, 4.5}
B. {-1, 2, 5, 7.5}
C. {-2, 4, 10, 15}
D. {-4, -1, 2, 4.5}