Two friends are considering launching their own car company. They have drafted a budget for the period January-December 2017. Rent expenses are estimated at 9.200, depreciation of equipment is estimated at 7.000, salaries are estimated at 16.400 and cost of engine oil is estimated at 2 per litre. According to the budget, each car will use at average 5 litres of engine oil with each vehicle inspection and each oil filter costs 3 per a car. Franchise fee is 1,1 for each oil change. The budget estimates the following electricity expenses in connection to the number of oil changes.

Number of oil changes	Electricity expenses
4.000	6.000
6.000	7.300
9.000	9.600
12.000	12.600
14.000	15.000

The two friends are going to sell their service at a cost of 25 per a car where the oil filter is included in the price.

1) Find the cost function for the electricity usage according to the high-low method.

2) Calculate the cost-volume-profit according to the budget, where revenues and expenses come together both in quantity and values.

3) How much do the two friends need to sell to profit 20.000?