CMW$,$ a custom metalwork shop, makes a variety of products from three basic inputs$$bar

stock, sheet metal, and rivets$$which are purchased in bars, sheets, and kits $($boxes of $100),$

respectively. Projected use and cost of these raw materials for the upcoming year are as

follows:

Use Cost

Part$(1,000$ units$/$year$)($$$/$unit$)$

Bar stock$12040$

Sheet metal$40020$

Rivet kits$1,0000\mathrm{.}5$

The shop estimates that issuing a purchase order for any type of material costs $$100$ and uses an interest rate of $15$ percent to calculate holding costs.

$($a$)$ Assuming steady use throughout the year, estimate the purchasing plus holding costs if all products are purchased four times per year. What happens to cost if we purchase each product $12$ times per year?