Two oxides of a metal contain 50% and 40% of metal M respectively.If the formula of first oxide is MO,+ve formula of $2^{nd}$ oxide will be

Question

$\begin{array}{1 1}(a)\;MO_2&(b)\;M_2O_3\\(c)\;M_2O&(d)\;M_2O_5\end{array}$