20 soliders are selected randomly. they run 2400 meters. the mean value for their results x=8.85 minutes and the variance s^2=30 seconds

a. calculate a 95% confidence interval for the mean basic fitness test result for the battalion

b. prove of disprove that eight out of 10 randomly selected solider can run 2400 meters in less than 8.6 minutes

if Z has a normal distribution with mean=0 and variance=1 the table gives P(Z≤z) for each value of z for negative values of z use 1-P(Z≤z)