A firm manufactures a product that sells for $$21$ per unit. Variable cost per unit is $$2$ and fixed cost per period is $$1520.$

Capacity per period is $1400$ units.

$($a$)$ Develop an algebraic statement for the revenue function and the cost function.

$($b$)$ Determine the number of units required to be sold to break even.

$($c$)$ Compute the break$-$even point as a percent of capacity.

$($d$)$ Compute the break$-$even point in sales dollars.

$($a$)$ The revenue function is $TR=$

$($Type an expression using $x$ as the variable. Do not include the $ symbol in your answer.$)$