$2-$ A $500-$foot long, $5-$foot$-$wide rectangular channel will carry water between spring$-$fed reservoirs. Flow depth cannot exceed $2$ feet and a minimum velocity of $5$ feet per second must be maintained. If the bottom elevation of the channel at the upper reservoir is $330$ feet, what is the maximum elevation of the channel bottom at the lower reservoir? Manning's $n$ for the channel is $0\mathrm{.}020.$