a) Sajina deposited Rs 20,000 at the rate of 8% p. a. in her saving account. After 2 years, she

a) Sajina deposited Rs 20,000 at the rate of 8% p. a. in her saving account. After 2 years, she withdrew Rs 5,000 and the total interest of 2 years. How long should she keep the remaining amount to get total interest of Rs 6,800 from the beginning?