Let S be the sum to n terms of an arithmetic progression. If S/3 = n/2(2a + (n - 1)d), then S equals _______.
a) 3a + n(n - 1)d
b) 3a + n(n + 1)d
c) 3a + n(n - 2)d
d) 3a + n(n + 3)d