A distributor of computer monitors purchases the monitors from an overseas supplier under a continuous review system. The average demand for a popular computer monitor is normally distributed with a mean of $50$ units a day and a standard deviation of $10$ units a day. It costs $$75$ to process each order, and there is a constant $16-$day lead time. The holding cost for each monitor is $$20$ per year, and the distributor wishes to maintain a $90\%$ service level $($z $=1\mathrm{.}28).$ The distributor operates $300$ days a year.

What is the reorder point R to satisfy a $90\%$ cycle$-$service level?