Answer
The graph is shown in the solution part.
Work Step by Step
A point of the graph is in the form $(t, N(t))$.
The answers to exercise 127 are
a. one person.
b. 10 persons.
Convert the answers into points on the graph.
a. At the initial moment ($t=0$) the number of persons who started the rumor is $1$, so $N(0)=1$. The corresponding point on the graph is $(0,1)$.
b. After $4$ minutes ($t=4$), the number of people who heard the rumor is $10$ ($N(4)=10$). The corresponding point on the graph is $(4,10)$
Now plot these points on the graph as shown below.
