Given z1 = 9+9 (square root) 3i and z2 = 2+ (square root) 3i, what is z2-z1?
a) 8+7 (square root) 3i
b) -7-8 (square root) 3i
c) 7+10 (square root) 3i
d) -7+10 (square root) 3i