'M' g of an element gave 'N' g of oxide.Equivalent weight of the element is

Question

$\begin{array}{1 1}(a)\;\large\frac{M+N}{M}\normalsize \times 8& (b)\;\large\frac{M}{N+M}\normalsize\times 8 \\(c)\;(N-M)\times 8&(d)\;\large\frac{M}{N-M}\normalsize\times 8\end{array}$