Suppose that the debt was completely paid after 4 years; then, 4 years of interest have passed.
The initial debt is $100000, and the interest is applied each year.
Year 1: 100000(1+r)
Where r is the interest rate.
Year 2: (100000(1+r))(1+r)=100000(1+r)^2
And so on.
Thus, after four years, the debt is:

Solving for r
![\begin{gathered} \Rightarrow(129750)/(100000)=(1+r)^4 \\ \Rightarrow1+r=\sqrt[4]{(129750)/(100000)} \\ \Rightarrow r=\sqrt[4]{(129750)/(100000)}-1 \\ \Rightarrow r=0.067276\ldots \\ \Rightarrow r\approx0.0673 \\ \Rightarrow r\approx6.73percent \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/f6i1s8un2h1f4dc37hrs0eltlxqcw9m7pj.png)
The answer is, approximately, 6.73%