Question4[21=4+8+6+3] Your company is developing a new type of concrete, but have been struggling to get the concrete's compressive strength, measured in MPa, to the level required. You are aiming for a design that results in a compressive strength of 54 MPa or higher. Four factors and their levels have been selected: A = relative humidity: 30% and 50% B = compaction: 80% or 90% C = age of concrete: 10 days or 20 days D = temperature: 280K or 300K These eight experiments have been run so far