Answer:
a. from the given graph, at y=4, x=0 which is the intercept on the y axis;

b. at x=4, the value of y=2

Step-by-step explanation:
Given the graph in the attached image;
y is a function of x;

We want to determine the value of x for which y=4 and also the value of y at x=4.
So, from the given graph, at y=4, x=0 which is the intercept on the y axis;

Also from the graph;
at x=4, the value of y=2
so;
