1 .
Arun invested a sum of money at a certain rate of simple interest for a period of four years. Had he invested the same sum for a period of six years, the total interest earned by him would have been fifty percent more than the earlier interest amount. What was the rate of interest percent per annum?
[ A ]    4
[ B ]    8
[ C ]    5
[ D ]    Cannot be determined
[ E ]    None of these
 Answer : Option D Explanation :