To form a complete monolayer of acetic acid on 1g of charcoal, 100 mL of 0.5M acetic acid was used. Some of the acetic acid remained unadsorbed. To neutralize the unadsorbed acetic acid, 40 mL of 1M NaOH solution was required. If each molecule of acetic acid occupies P x 10−23 m2 surface area on charcoal, the value of P is _____. [Use given data: Surface area of charcoal = 1.5 x 102 m2g−1 ; Avogadro’s number (NA) = 6.0 x 1023 mol−1 ]