7-2. An engineer suspects that the surface finish of metal parts is influenced by the type of paint used and the drying time. She selects two drying times-20 and 30 minutes-and uses two types of paint. Three parts are tested with each com- bination of paint type and drying time. The data are as follows: Drying Time (min) Paint 1 2 68 2223 20 30 74 78 64 85 50 92 92 66 86 45 85