$12$

$800$:$34$:$44$

A jewelry firm buys semiprecious stones to make bracelets an $600$ stones or more, $$8\mathrm{.}50$ per stone for orders of $400$ to $599$ operates $160$ days per year. Usage rate is $18$ stones per day,

a$.$ If carrying costs are $$1$ per year for each stone, find the orr intermediate calculations, except for order quantities whic answer to the nearest whole number.$)$