For an AP with first term a and sum of first m terms 0, the sum of next n terms will be

Question

$(a)\;\frac{a(m-n)n}{m-1}\qquad(b)\;\frac{-a(m+n)n}{m-1}\qquad(c)\;\frac{a(m+n)n}{m-1}\qquad(d)\;None\;of\;these$