In a polymer sample 30% molecules have a molecular mass 20,000,40% have molecular mass 30,000 and the rest have 60,000.Mass average and number average and number average molecular masses,respectively are

Question

$\begin{array}{1 1}(a)\;36666,43333\\(b)\; 43333,36000\\(c)\;36000,43333\\(d)\;43321,36666\end{array}$