A sum of money at simple interest amounts to $ 815 in 3 years and to $854 in 4 years. The sum is:  Choose the correct choice from the following answers:
A) $153
B) $698
C) $398
D) $549
E) $675
B   $698   S.I. for 1 year = $(854 - 815)= 
<gadget id="calculator">(854 - 815)</gadget>
<output>39</output>
$39.   S.I. for 3 years= $(39 x 3) = $117.   Principal = $(815 - 117)= 
<gadget id="calculator">(815 - 117)</gadget>
<output>698</output>
$698.
<result>B</result>
A sum of money at simple interest amounts to $ 815 in 3 years and to $854 in 4 years. The sum is: