2021 ONE(b)

The graph below shows the function $y=f(x)$.

For the function above:

(i) Find the value(s) of $x$ that meet the following conditions:

(1) $f^{\prime }(x)=0$:

(2) $f(x)$ is concave upwards:

(ii) What is the value of ${\lim }_{x\to 7}f(x)$:

State clearly if the value does not exist.