A professor is expected to cover $15$ chapters in an operations management text each semester. The class is scheduled to meet for one hour three times a week for $15$ weeks. During the fall she often discusses the previous and$/$or upcoming football game during class and as a result is only able to cover $13$ chapters. What is the best representation of the professor's labor productivity?

$\mathrm{.}30$ chapters per class

$0\mathrm{.}35$ chapters per hour

$0\mathrm{.}29$ chapters per hour

$\mathrm{.}87$ chapters per week