A retail store sells five types of products, P, Q, R, S, and T. The store's fixed costs are $90,000 per month. The variable costs per unit for product P, product Q, product R, product S, and product T are $12, $18, $24, $30, and $36 respectively. If the selling prices per unit for product P, product Q, product R, product S, and product T are $40, $50, $60, $70, and $80 respectively, how many units of each product must the store sell to maximize profit?