Sara is a lab manager in scott laboratory. if she buys a 3d printer for the lab, she has to pay the price which is $3500. then, she should pay $300 per year for the maintenance which would increase by 3% each year. sara could let other departments use the printer for their projects and earn $1000 each year. if she buys the printer, she will sell it for $500 after 5 years. the lab has 10% maar. what is the present worth of the printer. would you recommend buying the printer?

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.