Textbook Problem

Learning Curve The management of a factory finds that the maximum number of units a worker can produce in a day is 30. The learning curve for the number of units N produced per day after a new employee has worked for t days is modeled by

$N=30(1-e^{kt}).$

After 20 days on the job, a worker is producing 19 units in a day. How many more days should pass before this worker is producing 25 units per day?