Abicyclist leaves from her home at 9 a. m. and rides to a
beach40 mi away. because of a breeze off the ocean, thetemperature
at the beach remains 60 of throughout theday. at the
cyclist's home the temperature increases linearlywith time, going
from 60 of at 9 a. m. to 80of by 1 p. m. the
temperature is assumed to varylinearly as a function of position
between the cyclist's home andthe beach. determine the rate of
change of temperatureobserved by the cyclist for the following
conditions: (a) as shepedals 10 mph through a town 10 mi from her
home at 10 a. m.; (b) asshe eats lunch at a rest stop 30 mi from her
home at noon; (c)as she arrives enthusiastically at the beach at 1
p. m., pedaling 20mph.

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?