Part B(iii)
If B(iii) asks you to compare predictions from the model to estimates based on average rate of change, it is asking you to compare a line to the model. Be sure to:
Draw a picture. Label 𝑡-values. Label the line and the curve.
Mention concavity of the original model
Say "secant line" to refer to estimates based on average rate of change
Mention the 𝑡-values of the secant line
Mention the 𝑡-values the question is about
Mention which is on top for the relevant 𝑡-values.