A client host sends a W $=800-$byte file to a server which is L $=1200$ km away over a

B $=2\mathrm{.}5$ Gb$/$s optical fibre network.

$($i$)$ Calculate the upper bound of the link efficiency $($

LEUB

$)$ for this transmission

assuming that the speed of light in optical fibre is c $=200,000$ km$/$s$.$Calculate the necessary size of the file W which will allow to achieve a $50\%$

LEUB

for a link you considered in part $($i$)$