Use the stem-and-leaf plot shown. What is the mean time (to the nearest minute) that is spent waiting at the doctor's office?

0 I 7
1 l 5 8
2 l 4 9 9
3 l 0 1 6
4 l 5 8
5 l
6 l 1
7 l 3

A-29 minutes
B-31 minutes
C-34 minutes
D-37 minutes