3.91: Linear law: $\mathrm{e}^{y}$ against $x^{3}$

Variables $x$ and $y$ are such that when $\mathrm{e}^{y}$ is plotted against $x^{3}$, a straight-line graph is obtained. This line passes through the points $(1, 13.5)$ and $(7.5, 0.5)$.