A watermelon initially at $35C$ is to be cooled by dropping it into a lake at $15C.$ After $4$ h and $40$ min of cooling, the center temperature of the watermelon is measured to be $20C.$ Treating the watermelon as a $20-cm-$ diameter sphere and using the properties $k=0\mathrm{.}618\frac{W}{m}*K,=0\mathrm{.}15{10}^{-6}\frac{m^2}{s},=995k\frac{g}{m^3},$ and $c_p=4\mathrm{.}18k\frac{J}{k}g*K,$ determine the average heat transfer coefficient $(h)$ and the surface temperature of the watermelon at the end of the cooling period. $($use the Heisler chart learned from lecture note $26)$