Answer
See the detailed answer below.
Work Step by Step
$$\color{blue}{\bf [a]}$$
We know that the area under the $|\psi(x)|^2$ curve must equal 1.
So,
$$P(x)= \text{Area under the $|\psi(x)|^2$ curve}=1$$
where the graph is a triangle
$$\frac{1}{2}(8)c=1$$
Hence,
$$c=\color{red}{\bf 0.25}\;\rm cm^{-1}$$
$$\color{blue}{\bf [b]}$$
From the given graph, it is obvious that the particle is most likely to be found at $x=0$ cm.
$$\color{blue}{\bf [c]}$$
It is also obvious that about 75% of the areas under the curve of $|\psi(x)|^2$ is between $x=-2$ cm to $x=2$ cm.
$$-2\leq x\leq 2$$
$$\color{blue}{\bf [d]}$$
The probability density graph is the given graph, so we need to redraw it and shade the needed region, as shown below.
