Some researchers developing a new intelligence test are trying to decide how much time to allow to complete the test. The researchers have recorded the times (in minutes) for completion of 29 people who took the test for practice. The frequency distribution below summarizes the completion times recorded by the researchers. Time for completion (in minutes) Frequency 9 to 11 8 12 to 14 8 15 to 17 6 18 to 20 5 21 to 23 2 Based on the frequency distribution, using the midpoint of each data class, estimate the mean completion time of the people who took the test. For your intermediate computations, use four or more decimal places, and round your answer to one decimal place.