In a batch of 28 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) = {(0,0.54060), (1,0.38614), (2,0.07021), (3,0.00305)}Recall that the mean ? of a discrete random variable X with probability mass function f(x)=P(X=x) is given by ?= ?Xi.f(x?). Find ? for the probability mass function above. What does this number represent??= (Type an integer or decimal rounded to four decimal places as needed.)What does this number mean?PracticeA. This is the average number of defective units in each batch of 28 units.B. This is the probability that every 5 units tested will contain at least one defective unit.C. This is the expected number of defective units for every 5 units tested.D. This is the exact number of defective units in every 5 units tested.