a product cost $$4\mathrm{.}85$ and $15\%$ of all customers buy this product. And if $18$ customers come in per hour on the weekday $($ monday$-$ thursday$)$ and $30$ customers come in of the weekend $($Friday$-$Saturday$).$ The store is open $8$ hours on the weekdays and $12$ hours on the weekend. assume each month contains $4\mathrm{.}2$ weeks. What is the monthly revenue?