Suppose A1, A2, ….., A30 are thirty sets each having 5 elements and B1, B2 ………, Bn are n sets each with 3 elements, let ∪i=130 Ai=∪j=1n Bj=Sand each element of S belongs to exactly 10 of the Ai ’s and exactly 9 of the Bj ’s. Then n is equal to