An army enlistment officer categorizes potential recruits by IQ into three groups—class I: < 90, class II: 90–110, and class III: > 110. Given that the IQs in the population from which the recruits are drawn are normally distributed with μ = 100 and σ = 16, calculate the probability that of seven enlistees, two will belong to class I, four to class II, and one to class III.