For sample mean x = 150, sample size n = 36 and sample standard deviation s = 40 find 80% confidence interval for population mean.

For sample mean x = 150, sample size n = 36 and sample standard deviation s = 40 find 80% confidence interval for population mean.  Population standard deviation is not known, you should use formula on page 328 with  t-value from Appendix Table IV (use column  t0.10).