Athick casting initially at a uniform temperature of 150 c has properties of ρ=2790 kg/m3, k- 1.6 w/m-k and cp=956 j/kg-k. the surface of the casting is suddenly exposed to turbulent water at 20 c, giving a very large convective heat transfer coefficient a) using an explicit finite-difference scheme with 5x-6mm, determine the length of time required for the temperature 18 mm beneath the surface to change from its initial value. b) based on the results of your finite-difference solution, determine an approximate value for the heat (q") being convected from the surface after 1.5 minutes. c) sketch a plot of surface heat flux, q", as a function of time. the time obtained in part a of part a for the temperature 18 mm from the surface d) using to change from its initial value, check the temperature at that location (x=18 mm) using a different method.