25. A sum of money amouns to Rs. 850 in 3 years and Rs. 925 in 4 years. The sum is:

26. A lent Rs. 600 to B for 2 years and Rs. 150 to C for 4 years and received altogether from both Rs. 90 as simple interest. The rate of interest is:

27. The simple interest on a sum of money will be Rs. 600 after 10 years. If the principal is trebled after 5 years. What will be the total interest at the end of the tenth years?