A 9-cm-diameter potato $\left(\rho=1100 \mathrm{~kg} / \mathrm{m}^3, c_p=\right.$ $3900 \mathrm{~J} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}, k=0.6 \mathrm{~W} / \mathrm{m} \cdot{ }^{\circ} \mathrm{C}$, and $\alpha=1.4 \times 10^{-7} \mathrm{~m}^2 / \mathrm{s}$ ) that is initially at a uniform temperature of $25^{\circ} \mathrm{C}$ is baked in an oven at $170^{\circ} \mathrm{C}$ until a temperature sensor inserted to the center of the potato indicates a reading of $70^{\circ} \mathrm{C}$. The potato is then taken out of the oven and wrapped in thick towels so that almost no heat is lost from the baked potato. Assuming the heat transfer coefficient in the oven to be $40 \mathrm{~W} / \mathrm{m}^2 \cdot{ }^{\circ} \mathrm{C}$, determine (a) how long the potato is baked in the oven and (b) the final equilibrium temperature of the potato after it is wrapped.