If a principal of Rs. (x + 5000) is invested in SI at a rate of 12.5% per annum for 4 years earns Rs. (y + 4500) as the interest and Rs. (x + 2000) is invested in SI at a rate of 10% per annum for 4 years earns Rs. (y + 2000) as the interest. If Rs. (x + y) is invested in SI at a rate of 7.5% per annum for 6 years for SI, then find the interest obtained.