The scatterplot shows the time x (in hours) that a crystal was left in a solution and the mass y (in milligrams) of the crystal at the end of the time for 9 trials. The line of best fit for the data is also shown.
Using the slope of the line of best fit, which choice is closest to the crystal’s average growth rate, in micrograms per minute?
(Use 1 milligram =1,000 micrograms and 1 hour =60 minutes.)