Person A invested Rs.1500 in scheme P at 11.25% per annum rate of simple interest for 4 years and invested Rs.1200 in scheme Q at 25% per annum rate of simple interest for 'X' years. The interest received from both schemes is equal. If he invests Rs. 2000 in another scheme R at 4X% per annum rate of simple interest for 2 years then, find interest earned by him in scheme R.