Tough and good explanation please

Q2) A common bus in a computer system that connects 15 registers (each is 32 bits) and one memory unit with word size of 32 bits. 1. If the bus is designed using multiplexers, answer the following: a. What is the minimum number of multiplexers that are required? b. What is the minimum number of selection lines each multiplexer has? 2. If the bus is designed with three-state buffers and decoder(s), answer the following: a. What is the minimum number of three-state buffers that are required b. What is the minimum number of decoders shat are required c. What is the minimum size of the decoder