4. The top of a thin solid slab is exposed to oxygen from the air that reacts with the solid and produces solid oxide. The oxide extends from the surface, where that oxygen dissolves with a fixed concentration, and is transported by Fickian diffusion. The reaction rate is first order in oxygen concentration and exothermic with local heat generation governed by the local reaction rate. The slab starts at a uniform temperature and cools only by convection within a room maintained at a constant temperature. Assume that the density of the oxide (0x) and surface (s) are approximately equal and that the weight fraction of oxygen (O2)=0.1 (constant saturated O2 concentration at the surface). a. Develop dimensionless differential mass and energy balances and boundary conditions using the following dimensionless groups: 1=DABkL2=0.12=CPDABk=0.13=DABCpkL2Hrxn=104=khL=1t=L2DABt b. Using Mathematica plot the 3D profiles of O2,Ox, and T as functions of depth and time up to t=500 c. What is the physical meaning of these dimensionless groups and your plotted results