(a) The first three terms of an arithmetic progression are \(x\), \(5x-4\) and \(8x+2\). Find \(x\) and the common difference.

(b) The first three terms of a geometric progression are \(y\), \(5y-4\) and \(8y+2\).

(i) Find the two possible values of \(y\).

(ii) For each of these values of \(y\), find the corresponding value of the common ratio.