Air is heated in a 1-meter-long, 4 mm by 16 mm rectangular duct. the air inlet temperature is 27 °c and the air mass flow rate is 0.0003 kg/s. a uniform heat flux of 600 w/m^2 is imposed on the duct surface. determine the average temperature of the air and the surface temperature of the duct at the duct exit.

Ariver flows from north to south at 8 km/h. a boat is to cross this river from west to east at a speed of 20 km/h (speed of the boat with respect to the earth/ground). at what angle (in degrees) must the boat be pointed upstream such that it will proceed directly across the river (hint: find the speed of the boat with respect to water/river)? a 288 b. 21.8 c. 326 d. 30.2