What does each of the components in the function $Y=a+bx$ represent in cost behavior analysis?

Multiple Choice

$Y$ is the total cost, $a$ is the total fixed cost, $b$ is the variable cost per unit, and $x$ is the number of units produced.

$Y$ is the total revenue, $a$ is the selling price per unit, $b$ is the total variable cost, and $x$ is the number of units sold.

$Y$ is the total cost, $a$ is the variable cost per unit, $b$ is the total fixed cost, and $x$ is the number of units sold.

$Y$ is the per unit cost, $a$ is the fixed cost per unit, $b$ is the variable cost, and $x$ is the number of units produced.