A scientist is doing a study to determine the typical levels of carbon monoxide in the air of automotive garages. She measures the air quality at 8 different garages and gets the following result : 13 ppm, 26 ppm, 4 ppm, 36 ppm, 12 ppm, 19 ppm, 5 ppm, and 9 ppm. What is the mean of her data set ?

Question

$\begin{array}{1 1} (a)\; 14 \; ppm \\ (b)\; 14.5 \;ppm \\ (c)\; 15 \; ppm \\ (d)\; 15.5 \; ppm \end{array}$