Assume that you are trying to decide whether you should keep your presently owned car or purchase a new hybrid car. A new car will cost $30,000 and have annual operation and
maintenance costs of $1200 per year with a $10000 salvage value in 5 years (this is the estimated
economic service life). Your owned car has a resale value now of $6000; one year from now it
will be $4000, two years from now $3000, and 3 years from now $2200. Its operating cost is
expected to be $1900 this year, with costs increasing by $150 per year. You cannot use your
existent car longer than 3 more years. Assuming used cars like the one presently owned will
always be available, should you sell the presently owned car now, 1 year from now, 2 years from
now, or 3 years from now? Make the annual worth calculations at i=10% per year and show your
work.

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?