If $x is invested at a constant annually compound interest rate of k percent, what is the ratio of the total amount including interest after 7n years to that after 3n years?	Select:  A) (1+k/100)^n  B) (1+k)^n  C) (1+kn/100)  D) (1+k/100)^4n  E) (1+kn)
Amount after 7n years will be = x ( 1 + k/100)^4n   Amount after 3n years will be = x ( 1 + k/100)^3n   So, required ratio will be -   { x ( 1 + k/100)^7n } / {x ( 1 + k/100)^3n } = (1+k/100)^4n   Hence answer will be a. (1+k/100)^4n   (1+k/100)^4n
<result>D</result>
If $x is invested at a constant annually compound interest rate of k percent, what is the ratio of the total amount including interest after 7n years to that after 3n years?