For the first-order reaction $\text{A} \rightarrow \text{B}$, $\text{A}$ is optically active and $\text{B}$ is optically inactive. A series of experiments were conducted on a solution of $\text{A}$:

| Time (min.) | $0$ | $60$ | $\infty$ |
|---|---|---|---|
| Optical rotation | $82°$ | $77°$ | $2°$ |

Assume some impurity is present. Calculate the optical rotation after $5\,\text{hours}$. (Given $\ln 1.066 = 0.064$, $e^{0.16} = 1.17$)