Q1. A combination lock can be set to be open by any 4-digit sequence} where each digit is one of 0, 11 2, 3: 4, 5} 61 7, 8, 9. Digits can be repeated. Answen with justication, the following. (a) How many sequences are possible? (1)) How many sequences are possible if the first digit must be a 5'? (c) How many sequences are possible if the sequence cannot include a 5 in any position? ((1) How many sequences are possible if the sequence must include at least one 5