Current inventory is $90$ units. Current capacity is $860$ units per month. The average salary of production workers is $$1,300$ per month. Material costs $$140/$unit$.$ Each production worker accounts for $30$ units per month. Overtime is paid at time and a half. Any increase or decrease in the production rate costs $$45/$unit for tooling, setup, and line changes. This does not apply, however, to overtime. Inventory$-$holding costs are $$39$ per unit per month. Lost sales are valued at $$65$ per unit.