Question 1: 
In the sample chart, we show a rate of change of about –.00328 mmol/L
at 9:00 am. What does this mean about the CO_{2} concentration at
9:00 am? 
Answer: 
This means that the CO_{2} concentration is decreasing by .00328 mmol/L
per hour at 9:00am. (We would estimate that after another hour, we would
have a concentration which is about .00328 mmol/L lower.) 


Question 2: 
Based on the data in the chart, is the concentration of CO_{2}
increasing or decreasing at 9:00 am? How can you tell this from your data? 
Answer: 
The value you have for a rate of change at 9:00 am is negative, and
therefore the concentration is decreasing at 9:00 am. Don't
be fooled by the fact that the graph you see is increasing; the graph you
have plotted is of the rate of change of concentration, not of
the concentration itself. (In other words, your data is the derivative of
the concentration.) 