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 128 are
a. one person.
b. 18 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 $6$ minutes ($t=6$), the number of people who heard the rumor is approximately $18$ ($N(6)=18$). The corresponding point on the graph is $(6,18)$.
Now plot these points on the graph as shown below.
