Greene's Toys produces and sells 4,000 dolls per month with the following costs:

Variable costs:	$1.25 per doll
Fixed costs:	$3,300 per month

Greene recently switched vendors and expects variable costs to rise by $0.80 per unit. However, with a new lease on the factory, Greene expects fixed costs to drop by $200 per month.

After making the changes, what is Greene's cost equation used to estimate total monthly costs?