Apply the problem-solving strategy to find the simple interest earned given the principal, rate of interest, and time.

Problem: Susana invested a principal of $36,000 in her bank account that earned simple interest at an interest rate of $6.5\%$. How much interest did she earn in $3$ years?

1. Identify what to find: the simple interest.
2. Name the unknown: Let $I$ = interest.
3. Translate into an equation using the simple interest formula $I = Prt$. Given $P = 36{,}000$, $r = 0.065$, and $t = 3$: $I = (36{,}000)(0.065)(3)$
4. Solve the equation: $I = 7{,}020$
5. Answer: The interest Susana earned is $7,020.