I need help in this question part a,b, and c

ISP #1 provides exclusive Internet connectivity to ISP #2 with customers A, B, C and D. a) Suppose ISP #2 is given the range 195.128.0.0 to 195.128.255.255. ISP #2 turns around and allocates the entire range to its four customers A, B, C, D. List the four allocations ISP #2 makes to A, B, C and D in the prefix/mask notation. b) In the set-up above suppose ISP #2 is only given 195.195.0.0 to 195.195.23.255 and has only two customers A and B to allocate the entire range to in contiguous, equal sized chunks. List the allocations ISP #2 makes to A and B. Note that multiple prefix/mask allocations will be needed for each customer. c) For the case where ISP #2 is given 195.195.0.0 to 195.195.23.255, list the minimal number of routes ISP #2 needs to advertise to ISP #1