T $18\mathrm{.}7-2.$ A newspaper stand purchases newspapers for $$0\mathrm{.}55$ and sells them for $$0\mathrm{.}75.$ The shortage cost is $$0\mathrm{.}75$ per newspaper $($be cause the dealer buys papers at retail price to satisfy shortages$).$ The holding cost is $$0\mathrm{.}01$ per newspaper left at the end of the day. The demand distribution is a uniform distribution between $50$ and $75.$ Find the optimal number of papers to buy.