An electric car manufacturing company currently employs 100 workers and has capitol investment of $10 millions per month. The number of cars the company produces each month can be approximated by LaTeX: f(x,y)=5x^{0.2}y^{0.8}f ( x , y ) = 5 x 0.2 y 0.8. The average worker monthly salary is $10000, and each unit of capital costs $6000 per month. Due to a high demand of electric cars, the CEO decides to increase production up to 3000 each month. Find the objective function to minimize the cost of production.