According to a 2014 Kaiser Family Foundation Health Benefits Survey released in 2015, the total mean cost of employer-sponsored family health coverage was $16,834 per family per year, of which workers were paying an average of $4823. Suppose that currently the distribution of premiums paid by all workers who have employersponsored family health coverage is approximately normal with the mean and standard deviation of $4823 and $700, respectively. Let x be the average premium paid by a random sample of certain workers who have employer-sponsored family health coverage. Calculate the mean and standard deviation of x and describe the shape of its sampling distribution when the sample size is

a. 20 

b. 100 

c. 800