The revenue, cost, and profit functions for a line of cell phone cases is shown. Identify the location on the profit function where the profit from sales of the phone cases is a maximum.
y4
+2,500,000
+2,000,000
R(x)
F1,500,000
C(x)
Total (dollars)
+1,000,000
P(x)
-500,000
10
60
70
20 30 40 50
Price per Phone Case (dollars)

For a science project, a high school research team conducted a survey of local air temperatures. based on the results of the survey, the found that the average temperatures were around 10 degrees higher than expected. this result was wrong. the trouble with the survey was that most of the locations were exposed to direct sunlight and located over asphalt or sand, which resulted in higher temperatures than normal. this is a classic example of an error in which phase of inferential statistics?