An amount of Rs 10000 is deposited in bank A for a certain number of years at a simple interest of 5% per
annum. On maturity, the total amount received is deposited in bank B for another 5 years at a simple
interest of 6% per annum. If the interests received from bank A and bank B are in the ratio 10 : 13, then the
investment period, in years, in bank A is