A sum of money at simple interest amounts to Rs.720 after 2 years and to Rs.1020 after a further period of 5 years. The sum is :  Select the correct option:
A) 400
B) 500
C) 600
D) 700
E) 800
SI of 5 year = (1020-720)= 
<gadget id="calculator">(1020-720)</gadget>
<output>300</output>
300   so, SI of 1 year=300/5= 
<gadget id="calculator">300/5</gadget>
<output>60</output>
60   so, SI of 2 year=60*2= 
<gadget id="calculator">60*2</gadget>
<output>120</output>
120   so, sum is=(720-120)= 
<gadget id="calculator">(720-120)</gadget>
<output>600</output>
600   ANSWER:600
<result>C</result>
A sum of money at simple interest amounts to Rs.720 after 2 years and to Rs.1020 after a further period of 5 years. The sum is :