Pihu and Monu started a business with investments of Rs. 3,840 and Rs. 4,800, respectively. After 9 months, Monu exited the business. Pihu, as the active partner, is entitled to 20% of the total profit, while the remaining profit is distributed between them in proportion to their investments. If Pihu's total earnings at the end of 15 months amount to Rs. 1,150, determine Monu's share of the profit.