A fungus that spreads on a dish

A mould colony on a dish of agar has a radius of $3$ mm on day $0$, and its edge moves out $4$ mm every day. The dish has a radius of $45$ mm. You will find the radius and the area of the colony each day, and the first day it reaches the edge. Then the program draws both.

The idea. The radius grows by the same amount each day, but the area, $\pi r^2$, grows faster and faster. The colony cannot grow past the edge of the dish.

Your tasks.

1. Set radii to the radius on each day in days, in mm, never more than DISH.
2. Set areas to the area of the colony on each day, in mm².
3. Set first_full to the first day on which the radius equals DISH.