Applications with substitution In the following exercises, you must integrate by hand (i.e., show any substitution, the antiderivative, and the evaluation). 13. Suppose the rate of change in the temperature of the glass portion of a newly crafted telescope mirror is given by T'(t) = -9e, where 7 is in Celsius and t is in days since coming out of the furnace. Suppose the temperature of the telescope mirror is initially 1500' C. a. What will the temperature be after 28 days? Round to 2 decimals. b. How long, to the nearest day, will it take for the telescope mirror to cool to 1300 C