Answer:
18 minutes rounded to nearest integer
Explanation:
The relation between the temperature of steel in °F and time elapsed is

where
t is in minutes, C and k are constants
At time t = 0, f(t) = 2500
Plugging these values into the expression:

Therefore,

Temperature after 2 minutes = 1500 °F
Plugging these values into the function we get

Taking natural logs on both sides:



The function therefore is

to find out how many minutes it will take for the temperature to be 100 degrees we substitute 100 for f(t) and solve for t



