P$20.$ Consider the throughput example corresponding to Figure $1\mathrm{.}20($b$).$ Now suppose that there are $M$ client$-$server pairs rather than $10.$ Denote $R_s,R_c,$ and $R$ for the rates of the server links, client links, and network link. Assume all other links have abundant capacity and that there is no other traffic in the network besides the traffic generated by the $M$ clientserver pairs. Derive a general expression for throughput in terms of $R_s,R_c,R$ and $M.$