Obligatory problem for all students to solve. Consider a packet of length L that beginsat end system A and travels over three links to a destination end system B$.$ These threelinks are connected by two packet switches. Let di$,$ si$,$ and Ri denote the length,propagation speed, and the transmission rate of link i$,$ for i $=1,2,3.$ The packet switchdelays each packet by dproc. Assuming no queuing delays, in terms of di$,$ si$,$ Ri$,($i $=1,2,3),$ and L$,$ what is the total end$-$to$-$end delay for the packet? Suppose now the packet is$1,500$ bytes, the propagation speed on all three links is $2\mathrm{.}5108$ m$/$s$,$ the transmissionrates of all three links are $2\mathrm{.}5$ Mbps$,$ the packet switch processing delay is $3$ msec, thelength of the first link is $5,000$ km$,$ the length of the second link is $4,000$ km$,$ and thelength of the last link is $1,000$ km$.$ For these values, what is the end$-$to$-$end delay?$($textbook Problem $10).$ADDITIONAL QUESTIONS FOR GRADUATE STUDENTS$2.$ In the above problem, suppose R$1=$ R$2=$R$3=$ R and dproc$=0.$ Further, suppose the packet switchdoes not store$-$and$-$forward packets but immediately transmits each bit it receives beforewaiting for the entire packet to arrive. What is the end$-$to$-$end delay? $($Textbook problem $11).$