Andrew is investigating how long his phone's battery lasts (in hours) for various brightness levels (on a scale of 0-100). His data is displayed in the table and graph below.

Brightness Level (x)	Hours (y)
27	6.9
51	4.3
64	5.1
75	3.1
84	1.3
86	2.3
88	3.3
96	2.4

(a) Find the equation for the line of best fit. Round values to 2 decimals in the equation.

(b) Interpret the slope in context.

• Andrew expects the brightness to decrease by 0.07 for every hour that goes by.
• Andrew expects the brightness to go down by 1 every time the hours increase by 0.07

(c) What does the equation predict for the number of hours the phone will last at a brightness level of 64? Round to 1 decimal place. hours

(d) What is the residual for the point (64,5.1)? hours

(e) Interpret the meaning of the residual.

• At a brightness level of 64, the model predicted a battery life that is 1.1 hours different than the observed battery life in reality.
• At a brighness level of 64, the model predicts the battery to last 1.1 hours.
• At a brightness level of 64, the battery lasted 1.1 hours in reality.