Thus, the overall process has four input parameters i.e. the growth figures 10%, 5% and the time points 3 and 7.

Noting that – for any single time period in the model – there are exactly three possible cases for the “time bracket” in which it is i.e:

- Before period 3 (before the first time point).
- After period 7 (after the second time point).
- Between period 3 and period 7 (between the first and second time points).

In fact, since the formula used to calculate the growth between period 3 and period 7 is an “interpolation” formula, it makes no difference if “before period 3” is considered to include period 3, or whether period 3 is considered to be “between period 3 and period 7” (and similarly for period 7): TheÂ formula is designed to give the same value in either case. In other words, as shown in the following image, the growth rate is considered to be a continuous function of time: