四、 Calculation Problems ( 20 Score)
1.
It is known that the demand function of a certain commodity in a certain period
is Qd = 500-50p, and Qd represents the freight transport demand; The supply
function is Qs = -100+50P, Qs stands for quantity of transportation supply, and P
stands for freight price.
(1) Obtain equilibrium price Pe and equilibrium quantity Qe.
(2) The Point elasticity Ed of demand price when P= 2.
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Along 8-cm diameter steam pipe whose external surface temperature is 900c connects two buildings. the pipe is exposed to ambient air at 70c with a wind speed of 50 km/hr blowing across the pipe. determine the heat loss from the pipe per unit length. (b) air at 500c enters a section of a rectangular duct (15 cm x 20 cm) at an average velocity of 7 m/s. if the walls of the duct are maintained at 100c. a) the length of the tube for an exit temperature of the air to be 40 0c. b)the rate of heat transfer from the air. c) the fan power needed to overcome the pressure drop in this section of the duct.