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

Rationale: "s . i for 5 years = $ 595 - $ 420 = $ 175 the s . i . is $ 35 / year s . i . for 2 years = $ 70 principal = $ 420 - $ 70 = $ 350 the answer is e ."
Answer: E