Then let's try using a rectangle with a smaller ratio:
Then:
If you used a square:
There you have it. A rectangle with a smaller area with the same perimeter. What does it show? The smaller the difference you get from width and length, the larger the area is.
I think the equation is written wrong because assuming that his wage increases at the end of each year, the beginning of the first year wages should be 7.72, not 0.