Question 157726
Simple interest tells you that the annual interest the good Dr paid is 240/3.5 (the total interest divided by the 3.5 year term of the loan). That means Dr S is paying $70/year in interest.

Given an interest rate of 3.5%, we see that
{{{70 = Principal * 0.035}}}
{{{ 70/0.035 = P}}}
{{{2000 = P }}}

Check your answer. 
In the first year, the Dr pays 70.
In the second, 70 more
In the third, yet another 70.
Then for 1/2 year, the Dr pays 70/2 = 35.
For a total of 70+70+70+35 = 245