The following table shows the waiting times of 135 aircrafts and their frequencies at a certain airport. Aircraft waiting time (in minutes), for a departing aircraft is defined to be the difference...

Extracted text: The following table shows the waiting times of 135 aircrafts and their frequencies at a certain airport. Aircraft waiting time (in minutes), for a departing aircraft is defined to be the difference between scheduled departure time and actual departure time. Waiting Time (Minutes) 0 - 20 20 - 40 40 - 60 60 - 80 80 - 100 100 - 120 Number of Aircrafts 25 72 13 ? a. Compute the average waiting time. Answer in exact fraction, or rounded to at least 4 decimal places. b. Compute the median waiting time. Answer in exact fraction, or rounded to at least 4 decimal places. c. Determine the modal waiting time. Answer in exact fraction, or rounded to at least 4 decimal places.