Answer:
At the end of three years she would have $4,960. (4,000+960)
From all the calculations i did, it seems somewhere between .66% and .67% is the interest rate because it comes close to the 960 amount. but i dont know for sure.
(im using the .66% percent for this last question) so first i added the 1% to the .66% so that makes 1.66%. you then would multiple that percent by 4,000 so it sums up 66.4. multiple 66.4 by 36 (3 years is 36 months) and you get 2,390.40 you would lastly subtract 960 from 2,390.40 and get 1,430. so she would of had $1,430 more if the interest rate was 1% greater.
(I know the answers may be wrong but i know the process(steps) are correct)