Answer:
5605.01 dollars
Explanation:
Given that after 3 years your brother will pay your 7100 dollars.
If invested otherwise, interest is 8.20 percent per year
Let P be the amount invested
Then after 3 years at compound interest final amount
A =
![P(1+(8.2)/(100))^3\\ =P(1.082)^3](https://img.qammunity.org/2020/formulas/mathematics/college/engw3wcwew33vuy90k1lobcz9ffizh90qj.png)
This must be less than or equal to 7100 if willing to lend to brother
i.e.
![P(1.082)^3 \leq 7100\\P\leq 5605.01](https://img.qammunity.org/2020/formulas/mathematics/college/y2l6ry2y166fufn8ydog661lu3btet67qr.png)
So willing to lend upto 5605.01 dollars