Canoeing during heat wave

On vacation with your friend Sibylle, you are canoeing on a river whose water level decreased a lot because of multiple heat waves. When the water level falls below $20$ cm, you have to pull the canoe, or even lift it. As Sibylle is not exactly a body builder, you know that you’ll be the only one to pull the canoe and you want to be psychologically prepared.

The level of water (in meters) is given by the function $f$ such that:
$$f(x):=\exp\left(-\displaystyle\frac{1}{(x^2-4x+3)^{2}}\right),$$where $x\geqslant0$ stands for the distance in km from the starting point of your canoe trip.

1. Show that $f$ is extendable by continuity on $[0,8]$. In the following questions, we consider $f$ on this interval.
2. At which moment(s) of the ride will the water level be minimal?
3. On which total distance will you have to pull the canoe, during your $8$ km ride?

Data : $\exp(-1)\simeq0.37$