Peter invested an amount of Rs 12,000 at the rate of 10 p.c.p.a. simple interest and another amount at the rate of 20 p.c.p.a. simple interest. The total interest earned at the end of one year on the total amount invested became 14 p.c.p.a. Find the total amount invested. (a) Rs 20,000    (b) Rs 22,000    (c) Rs 24,000    (d) Rs 25,000