A manufacturer of handcrafted wine racks has determined that the cost to produce $x$ units per month is given by $C=0\mathrm{.}3x^2+7,000.$ How fast is the cost per month changing when production is changing at the rate of $10$ units per month and the production level is $60$ units?

Costs are at the rate of $ per month at this production level.

$($Round to the nearest dollar as needed.$)$