Answer: The required time needed to deliver 72 papers is 2 hours 24 minutes.
Step-by-step explanation: Given that 9 papers are delivered in 18 minutes.
We are to determine the time needed to deliver 72 papers.
We will be using the UNITARY method to solve the problem.
We have
Time needed to deliver 9 papers = 18 minutes.
So, time needed to deliver 1 minute will be

Therefore, time needed to deliver 72 papers is given by

Thus, the required time needed to deliver 72 papers is 2 hours 24 minutes.