Step-by-step explanation
Part A
When the number of hours = 9.9, the observed amount is given as 21.50. The predicted amount can be gotten using the equation of the line of best fit.

Therefore, the residual amount becomes

Part B
When the number of hours = 12.1, the observed amount is given as 25.00. The predicted amount can be gotten using the equation of the line of best fit.

Therefore, the residual amount becomes

Answer: