Question
A1,A2,A3,...,A30 be thirty sets with 5 elements and B1,B2,...,Bn be n sets each with 3 elements. If C is a set containing m elements such that each element of C belongs to exactly 10 of the A′is and exactly 9 of the B′js and C=30∪i=1Ai=n∪j=1Bj, then find the number of positive integral solutions of equations of equation x1+x2+...+x15=45