Probability Distribution Function (PDF) for a Discrete Random Variable · Exercise 9

A baker is deciding how many batches of muffins to make to sell in his bakery. He wants to make enough to sell every one and no fewer. Through observation, the baker has established a probability distribution.
$$\begin{array}{cc}\text{x}& \text{P(x)}\\ \text{1}& \text{.15}\\ \text{2}& \text{.35}\\ \text{3}& \text{.40}\\ \text{4}& \text{.10}\end{array}$$

On average, how many batches should the baker make?

OpenStax, Statistics · §4.1 Probability Distribution Function (PDF) for a Discrete Random Variable · Exercise 9