Over the past 4 years, the height of a tree increased at a constant rate of 15% per year. It is known that the present height of the tree is 8 m. (a) What was its height 4 years ago? (b) Find the increase in its height over the past 4 years. (Give the answers correct to the nearest 0.01 m.) 25. Bank X offers interest at 7% p.a. compounded yearly. Bank Y offers interest at 6% p.a. compounded monthly. Mr Ho is going to deposit $50 000 in one of the banks for 10 years. Explain (a) Which bank should he choose in order to earn more interest? Explain your answer. (b) Suppose the interest rate offered by bank Y changes to 6.8% p.a. Explain (i) Which bank should he choose in order to earn more interest? Explain your answer. (ii) When compared to the original interest rate of 6% p.a., how much more interest will be paid by bank Y now? 19. Mr Hung borrows a sum of money from a bank at an interest rate of 18% p.a. compounded every 2 months. If he has to pay an interest of $304.5 after 4 months, find the sum of money borrowed. 20. At the beginning of 2009, Miss Wong deposited a sum of money in a bank at an interest rate of 8% p.a. compounded yearly. If she received an interest of $12 480 at the beginning of 2011, find (a) the sum of money deposited, (b) the amount she received at the beginning of 2014. 21. Mr Wong deposits $2 000 000 in a bank, and he will receive a simple interest of $400 000 after 2 years. Afterwards, the amount obtained will be deposited in another bank at the same annual interest rate, but the interest will be compounded half-yearly. How much will he receive after 2 more years?