Your friend, Mr$.$ Wasim Akram has received Rs$.5$ million by selling a

portfolio of stocks that he had held for the last $10$ years. He wants to double

this fund by investing in a Fixed Deposit in Hexagon Bank. If Hexagon Bank is

offering an interest rate of $6\mathrm{.}50\%$ p$.$a$.$ with quarterly compounding, what is the

approximate time required for Wasim to double his fund?