If ratio of molecular masses of two radioactive substances is $\;\large\frac{1}{2}\;$ and ratio of decay constant is $\;\large\frac{5}{3}\;$ . Then ratio of their initial activity per mole will be

Question

$(a)\;\large\frac{4}{3}$$\qquad($$b)\;\large\frac{5}{3}\qquad($$c)\;$$3\qquad(d)\;\large\frac{2}{3}$