The formula to calculate the percentage change is:



The answer to the constant increase in the montly rate is : 34.69 (average)
Given R(26)=0.72
The function will be:

using 0.72 as base:

Solving for b
![\begin{gathered} (0.80)/(0.72)=b^(29) \\ b=\sqrt[29]{1.11}=1.00 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/q1wj9qdfkw7bixdf40jhgh8o0r35e46tv1.png)
The function will be:

Where x is the mid-interval.