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Justify each product rule or sum rule you use to prove the following: a. What is the number of elements in the Cartesian product of sets A (cardinality: n) and B (cardinality: m) b. Suppose statement labels in a programming language can be either a single letter or a letter followed by a digit. Find the number of possible label. c. How many bit strings of length eight either start with a 11 bit or end with the two its 00