Problem 4 (15 points) Cracking is a process in which large hydrocarbon molecules are broken up "cracked" into smaller, more valuable hydrocarbon molecules. The cracking of petroleum hydrocarbons was originally done by thermal cracking. Now, catalytic cracking offers a greater economic value than the gases produced by thermal cracking. Assume in a catalytic cracking regenerator, catalytic particles at 600C are injected into air at 700C in a fluidized bed. The specific heat of the particle is 1090 J/kg. C, the density is 960 kg/m), and the thermal conductivity is 2 W/m.C. Assume the heat-transfer coefficient of air is 2698 W/m2.C. Neglecting the chemical reaction, how long will it take for a 50-um particle to be heated to 695C? State the figure or Equation used in your calculations