A sum of money lent out at S.I. amounts to a total of $420 after 2 years and to $595 after a further period of 5 years. What was the initial sum of money that was invested?  Choose the correct choice from the following answers
A) $310 B) $320 C) $330 D) $340 E) $350
S.I for 5 years = $595 - $420 = $175   The S.I. is $35/year   S.I. for 2 years 595 -  420= 
<gadget id="calculator">595 -  420</gadget>
<output>175</output>
$175   The S.I. is $35/year   S.I. for 2 years= $70   Principal = $420 - $70 = $350   The answer is $350.420 -  70= 
<gadget id="calculator">420 -  70</gadget>
<output>350</output>
$350   The answer is $350.
<result>E</result>
A sum of money lent out at S.I. amounts to a total of $420 after 2 years and to $595 after a further period of 5 years. What was the initial sum of money that was invested?