Can someone help me? Thanks. Saiyaa and Aubrey are evaluating antimicrobial efficacy of lemongrass. After Soxhlet extraction and evaporation of the lemongrass extract, they obtained the phytochemicals in a powder form. They constituted Stock solution by adding 250mg of the extract (phytochemicals) in 1.0mL solvent. - Express the concentration of the stock solution as "percentage solution (w/v). - Calculate the volume of the stock solution required to prepare the following 2.5mL of working solution (40mg/mL ). (working solution).