Suppose a pizza parlor has the following production​ costs: ​$ in labor per​ pizza, ​$ in ingredients per​ pizza, ​$ in electricity per​ pizza, ​$ in restaurant rent per​ month, and ​$ in insurance per month. Assume the pizza parlor produces pizzas per month. What is the variable cost of production​ (per month)? The variable cost of production is ​$ nothing. ​(Enter your response as an​ integer.)