Josh 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)
20	4.6
23	4.3
38	7
59	2.3
72	2.8
72	4.1
73	2.7
93	2.1

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

(b) Interpret the slope in context.

• Josh expects the brightness to go down by 1 every time the hours increase by 0.04
• Josh expects the brightness to decrease by 0.04 for every hour that goes by.

(c) What does the equation predict for the number of hours the phone will last at a brightness level of 38? Round to 1 decimal place. hours

(d) What is the residual for the point (38,7)? hours

(e) Interpret the meaning of the residual.

• At a brighness level of 38, the model predicts the battery to last 2.5 hours.
• At a brightness level of 38, the battery lasted 2.5 hours in reality.
• At a brightness level of 38, the model predicted a battery life that is 2.5 hours different than the observed battery life in reality.