Jacob has a bank account which pays compound interest at a rate of x% per year. The amount of money in Jacob's bank account at the end of each year forms a geometric sequence. The table below shows the amount of money in the account at the end of the first two years.
a) Work out an expression for the amount of money, in pounds (£), in Jacob's bank account after n years. Give your answer in the form a X f(n-1), where a and r are numbers.
b) Work out the compound interest rate, x%.
c) How much money did Jacob put into his bank account to start with? Give your answer in pounds (£).