$($c$)$ Reservoir A $($water level $225m$ AOD$)$ is connected to reservoir B $($water level $185m$

AOD$)$ by a $600mm$ diameter pipeline of $2\mathrm{.}5km$ long. To increase the discharge from $A$

to $B$ by $50\%$ it is proposed to lay a second $600mm$ diameter pipe, parallel and close to

the existing, from point $A$ to a point $C$ part way along $AB,$ where the two pipes will be

joined. What is the minimum length of AC$.?$ Take Hazen$-$Williams C value for both

pipelines as $120$ and ignore minor losses.

$15$ Marks