Mt. McKinley (Alaska) has an approximate elevation of 20,000 ft. (a) Determine the pressure at this elevation (in "psia"), using the standard atmosphere model. (b) If (hypothetically) the air is assumed to have a constant specific weight of, approximately, 0.0765 lb/ft3, what would the pressure be at this elevation (in "psia")? (c) If (hypothetically), the air is assumed to have a constant temperature of 520 R, what would the pressure be at this elevation (in "psia")