In a meat processing plant, 2-cm-thick steaks (k=0.45 W/m⋅K and α=0.91×10−7 m2/s) that are initially at 25∘C are to be cooled by passing them through a refrigeration room at −11∘C. The heat transfer coefficient on both sides of the steaks is 9 W/m2⋅K. If both surfaces of the steaks are to be cooled to 2∘C, determine how long the steaks should be kept in the refrigeration room. Solve this problem using the analytical one-term approximation method (not the Heisler charts). I'm confused about how I can get the Fourier number. I got the Bi which is 0.2, which I used to get α1λ1 and α1A1, but how should I calculate the Fourier number? Please explain so I can understand how to do it on my own.