What concentrations of CellROX® Deep Red Reagent, N-acetylcysteine (an antioxidant for negative control), and Tert-butyl hydroperoxide (for positive control) should be prepared to effectively stain Human Epidermal Keratinocytes (adult) cultured in a 6-well plate with a cell density of 5*10^5 cells/well? Additionally, is a 37°C incubation condition suitable for the HEKa cell line during the staining procedure?