Ernie and Burt both make pizzas for a living. Making a pizza consists of two tasks: making the crust and applying toppings. Ernie can make crusts at the rate of 30 crusts per hour. He can apply toppings at the rate of 15 toppings per hour. Burt can make crusts at the rate of 15 crusts per hour. He can apply toppings at the rate of 30 toppings per hour. After years of operating separate, one-man shops, they realize they can produce more efficiently by combining operations and dividing the tasks between them. How many more pizzas per hour can they make if they work together and allocate tasks efficiently than they made when they worked separately?