Probability Distribution Function (PDF) for a Discrete Random Variable · Exercise 18

Suppose that the PDF for the number of years it takes to earn a Bachelor of Science (B.S.) degree is given in.

$$\begin{array}{cc}\text{x}& \text{P(x)}\\ \text{3}& \text{0.05}\\ \text{4}& \text{0.40}\\ \text{5}& \text{0.30}\\ \text{6}& \text{0.15}\\ \text{7}& \text{0.10}\end{array}$$

(a) In words, define the random variable X.
(b) What does it mean that the values zero, one, and two are not included for x in the PDF?

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Introductory Statistics 2e · §4.1 Probability Distribution Function (PDF) for a Discrete Random Variable · Exercise 18