Super is a ride-sharing company. The Chief of Operations wants the revenue (output value) to be seven times the cost of service operations (input cost). Suppose that each regular car earns a value of $1500 per month and premium cars earn $2500 per unit per month. The monthly cost of operating a regular car is $100 per month and $500 per premium car. Super currently has 19 regular cars. How many premium cars do they need to achieve a productivity ratio of 7? (Enter your response rounded to whole number.)​