A and B partnered to start a business with initial investments of Rs. 1,200 and Rs. 1,500, respectively. After one year, they both reinvested additional amounts, with A contributing Rs. 600 and B adding Rs. 1,000. At the end of two years, their combined profit amounted to Rs. 4,200. A choose to reinvest his share of the profit in a scheme offering a 10% annual compound interest for two years. How much interest did A earn from this investment?