(a) The first term of an arithmetic progression is \(3\). The sum of the first 10 terms is four times the sum of the first 5 terms. Find the common difference.

(b) The first, second and fifth terms of another arithmetic progression are the first, second and third terms of a geometric progression. The first term is non-zero. Find the common ratio of the geometric progression, where the common ratio is not \(1\).