If these drugs are to be screened for their cell proliferation and cytotoxic screening using CCK-8 assay, looking at two different parameters including (1) Varied concentration of the drug (2) Time (6 hrs, 12hrs, 24 hrs and 48 hrs). What could qualify anyone of these drugs as the best? What we are looking for here include (1) Safe dosages for subsequent cell assays and (2) The best time factor for culturing these cells in the course of the subsequent assays. Please, I really need your help. Thanks.