‘C’ and ‘D’ entered into a business by investing Rs. ‘y’ and Rs. ‘y + 300’, respectively. After 10 months ‘C’ invested Rs. 400 more and after 6 more months ‘D’ increased his investment by Rs. 800. If at the end of two years, the ratio of profit share of ‘C’ and ‘D’ was 15:18, respectively, then find the value of ‘y’.