'S' allocated 40% of his monthly income to SIP P, where it accrues a simple interest of 18% p.a. The remaining 60% was directed to SIP Q, with a compound interest of 20% p.a., compounded annually. After 2 years, the total amount gained from both SIPs matches the amount yielded by investing Rs. 6000 at 19% p.a. simple interest for 4 years. Calculate 'S's total monthly income.