In an adsorption batch test substance Y is dissolved in the solution with an initial concentration of 250 mg/L. 0.3524 gram of granulate activated carbon GAC was added to 50mL of such solution as well as had sufficient contact time with the solution. The substance Y solution now has a concentration of 25 mg/L. Explain what is the mass of substance Y that is adsorbed to the GAC? Explain what is mass to mass ratio of the adsorbed substance Y to GAC in mg/kg at this equilibrium concentration?