d $=$ N L$/$R is the formula for the end$-$to$-$end delay of sending one packet of length L over N links of transmission rate R$.$ Generalize this formula for sending P such packets back$-$to$-$back over the N links.d $=$ N L$/$R is the formula for the end$-$to$-$end delay of sending one packet of length L over N links of transmission rate R$.$ Generalize this formula for sending P such packets back$-$to$-$back over the N links.d $=$ N L$/$R is the formula for the end$-$to$-$end delay of sending one packet of length L over N links of transmission rate R$.$ Generalize this formula for sending P such packets back$-$to$-$back over the N links.