classroom pps " Gmail YouTube A Maps PlusPortals 4 IB Documents PES HL AA Mock Paper 2 Section B.pdf Open with 3. [Maximum mark: 13] On the day of her birth, 1st January 1998, Mary's grandparents invested Sr in a savings account. They continued to deposit Sr on the first day of each month thereafter. The account paid a fixed rate of 0.4% interest per month. The interest was calculated on the last day of each month and added to the account. Let S.4, be the amount in Mary's account on the last day of the nith month, immediately after the interest had been added. (a) Find an expression for A, and show that A, = 1.004 x + 1,004x. (b) (1) Write down a similar expression for A, and A, (1) Hence show that the amount in Mary's account the day before she turned 10 years old is given by 251(1.004)- 1)r. (c) Write down an expression for 4, in terms of x on the day before Mary turned 18 years old showing clearly the value of n. (d) Mary's grandparents wished for the amount in her account to be at least $20000 the day before she was 18. Determine the minimum value of the monthly deposit Sx required to achieve this. Give your answer correct to the nearest dollar