$11.$ The revenue function is R$($x$)=10$x $-\mathrm{.}001$ x$^2$

A$.$ What is the marginal revenue if we produce $2,000$ items $($x $=2000)?$

B$.$ What is the marginal revenue if we produce $5,000$ items $($x $=5000)?$

C$.$ What is the marginal revenue if we produce $7,000$ items $($x $=7000)?$