Mohit, Jatin, and Megha entered into a partnership with an initial investment of 'd' Rs., (d - 2000) Rs. and (d + 3000) Rs. respectively, and after 6 months Nikki joins with an investment of (d + 6000) Rs. Further, 6 months later both Mohit and Nikki again invested 3000 Rs. more into their business. If at the end of the two years, the total profit received by them is 267500 Rs. and the profit earned by Mohit is 7500 Rs. less than that of Megha then find the initial amount invested by Mohit?