Things did not go quite as planned. You invested $5,100.00, part of it in a stock that paid 4% annual interest. However, the rest of the money suffered a 4% loss. The total annual income from both investments was $36.00. For the following, use $x$ for the amount invested at 4% and $y$ for the amount that lost money.

a) Write a mathematical expression for the total amount of money invested.
Answer:

b) Write a mathematical expression for the total interest earned.
Answer:

c) How much money was invested at 4%?
Answer: