Aman, Bhanu, and Chikku jointly initiated a business with a total investment of Rs. 80,000, of which Aman invested Rs. 24,000. After 6 months, Aman added an additional Rs. 8,000 to his initial investment. Bhanu's investment was active for 8 months only. If, at the end of the year, the profit share between Aman and Bhanu is in the ratio of 7:6, determine the amount invested by Chikku.