Riel Company manufactures a varlety of tool boxes. The firm is currently operating at $80\%$ of its full capacity of $6,200$ machine$-$hours per month. Each unit requires $30$ minutes of machine time. Its sales manager has been looking for special orders to make productive use of the excess capacity. JCL Ltd$.,$ a potential customer, has offered to buy $10,000$ tool boxes at $$14\mathrm{.}30$ per box, provided that the entire quantity is delivered in two months. The current per$-$box cost data are as follows:

$\backslash$table$[[$Direct materials,$$4\mathrm{.}20$