Layers of 6-in-thick meat slabs (k = 0.26 Btu/hftF and = 1.4 10 -6 ft

Layers of 6-in-thick meat slabs (k = 0.26 Btu/h·ft·°F and α = 1.4 × 10^-6 ft²/s) initially at a uniform temperature of 50°F are cooled by refrigerated air at 23°F to a temperature of 36°F at their center in 12 h. Estimate the average heat transfer coefficient during this cooling process. Solve this problem using the Heisler charts.