I would like to get some help with this question please thank you

A-1-1. {10 marks} Let n 2 t 2 1 be postive integers. (a) Give a bijection f : A - B where . A is the set of multisets of size n with t types where every type has 1 or 2 elements, and . B is the set of subsets of {1, ..., {} of size n - t, and determine the size of A. (b) Give a bijection f : A - B where . A is the set of multisets of size n with t types where every type has an odd number of elements where n - t is even, and . B is the set of multisets of size ", with t types. and determine the size of A. In both of your solutions, you need to clearly define your bijection f : A + B, show that f(X) E B for all X E A, and write down the inverse of f. You do not have to prove that your inverse is correct