In a batch of 25 ​pedometers, 3 are believed to be defective. A​ quality-control engineer randomly selects 5 units to test. Let random variable X=the number of defective units that are among the 5 units tested. The probability mass function ​f(x)=​P(X=​x) is given below. ​f(x)=​{(0,0.49565​), ​(1,0.41304​), ​(2,0.08696​), ​(3,0.00435​)} Recall that the mean μ of a discrete random variable X with probability mass function ​f(x)=​P(X=​x) is given by μ=∑i=1nxi•fxi. Find μ for the probability mass function above. What does this number​ represent? μ=nothing ​(Type an integer or decimal rounded to four decimal places as​ needed.) What does this number​ mean? A. This is the probability that every 5 units tested will contain at least one defective unit. B. This is the expected number of defective units for every 5 units tested. C. This is the average number of defective units in each batch of 25 units. D. This is the exact number of defective units in every 5 units tested.