Assume that one 16 bit and two 8 bit microprocessors are to be interfaced to a system bus. The following details are given: (1) All microprocessors have a 16 bit address bus. (2) All microprocessors have the hardware features necessary for any type of data transfer: programmed I/O, interrupt driven I/O, and DMA. (3) Two memory boards, each of 64 Kbytes are interfaced with the bus. The designer wishes to use a shared memory that is as large as possible. (4) The system bus supports a maximum of four interrupt lines and one DMA line. Make any other assumptions necessary and: (a) Give the system bus specifications in terms of number and types of lines. (b) Describe a possible protocol for communicating on the bus. (c) Explain how the aforementioned devices are interfaced to the system bus.