The workers’ union at a certain university is quite strong. About 96% of all workers employed…

The workers’ union at a certain university is quite strong.
About 96% of all workers employed by the university belong to the
workers’ union. Recently, the workers went on strike, and now a
local TV station plans to interview a sample of 20 workers, chosen
at random, to get their opinions on the strike.

Estimate the number of workers in the sample who are union
members by giving the mean of the relevant distribution (that is,
the expectation of the relevant random variable). Do not round your
response.
Quantify the uncertainty of your estimate by giving the
standard deviation of the distribution. Round your response to at
least three decimal places.