A and B started a business by investing Rs. 2400 and Rs. 3600 respectively. At the end of 4^th month from the start of the business, C joined with Rs. 'X'. After 8 months from the start of the business, B withdrew Rs. 600. If C's share is Rs. 8000 in the annual profit of Rs. 22,500, what was the amount that C invested in the business?