Problem 2.1.The specified concrete strengthf′cfor a new building is 5000 psi. Calculate the requiredaveragef′crfor the concrete (a) if there are no prior test results for concrete with a compressive strengthwithin 1000 psi off′cmade with similar materials, ( b ) if 20 test results for concrete withf′c= 5500 psimade with similar materials produce a sample standard deviationssof 560 psi, and ( c ) if 30 tests withf′c= 4500 psi made with similar materials produce a sample standard deviationssof 540 psi.