Suppose the length of each packet is L bits. Also, assume the path from a server to a client includes N links each of rate R $($i$.$e$.,$ there are N$-1$ routers between the server and the client$).$a$.$ With store$-$and$-$forward packet switching, what is the end$-$to$-$end delay to transmit one packet over the N links $($ignoring propagation, processing, and queueing delays$)?$b$.$ What is the delay if the server sends P such packets back$-$to$-$back over the N links?