A random sample of 49 measurements from a population with population standard deviation σ1 = 4 had a sample mean of x1 = 9. An independent random sample of 64 measurements from a second population with population standard deviation σ2 = 5 had a sample mean of x2 = 12. Test the claim that the population means are different. Use level of significance 0.01. Find a 99% confidence interval for μ1 − μ2.