Use the exponential function to estimate the temperature

Question

y = 89.976 e ^{- 0.023 t} where t = Time Elapsed (minutes) and

y = Temperature Difference (in degrees)

(a) Use the exponential function to estimate the temperature difference y when 35 minutes have elapsed. Report your estimated temperature difference to the nearest tenth of a degree. Show work.

(b) How long will it take for the coffee to reach a temperature of 120 degrees? HINT: We first must find the value of y, which is C - 69. Therefore, y = 120 - 69 = 51. We now use this value of y=51 in the equation and then solve for t = time. Don't forget to follow the rules on solving an exponential equation. You are solving: 51 = 89.976 e ^{- 0.023 t}  : 51 = 89.976 e ^{- 0.023 t}