During the first week at a new job, krystal worked 7.5, 8, 7, 8.5, and 8 hours over the course of her five days.
in her second week, krystal worked 4 more hours than she had in her first week.
what was krystal's increase in mean number of hours worked per day from her first week to her second week?
0.8 h
1.25 h
8.6 h