Nearly 7,000 children acquired disease Z in the last year. Among the population of all children who acquired disease Z in the last year, suppose that (unknown to researchers) 1400 of them (20%) also acquired a secondary skin infection. A researcher intends to take a simple random sample of 50 children who had the disease last year and record whether or not the person also had a secondary infection. Let X be the number of children in the sample who report having a secondary infection. The variance of this distribution is .