A Novel Optimization of Feed and Spindle Speed Levels for Surface Roughness and Cylindricity Tolerance of the Drilled Holes in Liquid Stir Casted Al6061 Hybrid Metal Matrix Composite Reinforced with 15% Weight Fraction of B4C+Fly ash and Comparing with th. Journal of Pharmaceutical Negative Results. Published online September 27, 2022:438-449. doi:10.47750/pnr.2022.13.S04.048