Consider parallel surfaces that are opaque to thermal radiation. The horizontal surfaces are separated by a gap of thickness L = 0.12 m. The top surface is at tem- perature T and is coated with a high emissivity paint, & 1. The bottom surface is at temperature T and is characterized by: E = 0.1 E = 0.8 Ex 0 < < 10 m > 10 m (a) The enclosure formed by the surfaces is filled with air at atmospheric pressure with T = 500 K and T = 300 K. Determine the heat flux across the enclosure. (b) The enclosure is filled with liquid water at an average temperature of T = 300 K. There is a 5 K temperature difference across the enclosure with the bottom surface being hot. Determine the heat flux across the enclosure.