10. By investing in a 6% stock at 96, an income of Rs. 100 is obtained by making an investment of:

11. A man bought 20 shares of Rs. 50 at 5 discount, the rate of dividend being 4 %. The rate of interest obtained is:

12. Rs. 2780 are invested partly in 4% stock at 75 and 5% stock at 80 to have equal amount of incomes. The investment in 5% stock is: