If the sum of the first 7 terms of an arithmetic progression (AP) is 49 and that of the first 17 terms is 289, find the sum of the first n terms.
a) n(2a + (n - 1)d)
b) n/2(2a + (n - 1)d)
c) {n}/{2}(a + l)
d) n(a + l)