an opaque horizontal plate is well insulated on the edges and the lower surface. the irradiation on the plate is 3000 w/m2, of which 500 w/m2 is reflected. the plate has a uniform temperature of 700 k and has an emissive power of 5000 w/m2. determine the total emissivity and absorptivity of the plate. add: repeat assuming material is semitransparent with transmissivity of 0.10, the same reflectivity and the same emissive power.