Suppose $20$ packets, $500$KByte each, are sent from host A to host B across a network of $4$ routers. These

routers are separated by $10$ Mbps links that are $1000$m long each. Assume that the link propagation speed

is $2\mathrm{.}5\backslash$times $108$ m$/$s and there is no processing delay.

$($a$)(1$ point$)$ What is the transmission delay $($in msec$)$ of a single packet over the first link $($A$-$R$1)?$

$($b$)(1$ point$)$ What is the propagation delay over the link $($A$-$R$1)?$

$($c$)(4$ points$)$ What is the total end$-$to$-$end delay $($in sec$),$ i$.$e$.$ the time from which host A begins

sending the first packet until the time B finishes receiving the last packet?

$($d$)(4$ points$)$ Now suppose that each router will take $5$ msec to process each packet. What will be the

new end$-$to$-$end delay $($in msec$)?$