2 g of charcoal is placed in 100 ml of 0.5M CH₃COOH to form an adsorbed monoacidic layer of  acetic acid molecules and there by the molarity of CH₃COOH reduces to 0.49.The surface area of charcoal is $3\times {10}^2{\mathrm{m}}^2{\mathrm{g}}^{-1}$ The surface area of charcoal adsorbed by each molecule of acetic acid is, $\mathrm{x}\times {10}^{\mathrm{y}}\text{ then }\mathrm{y}-\mathrm{x}=$