A groundwater source is contaminated by Chemical X at a concentration of 31 g/L. You are hired as an environmental engineer to decrease that concentration to 10 g/L by adding activated carbon. According to the literature, the Freundlich isotherm coefficients for activated carbon are Kp = 0.02 L/mg and n = 2.9 for concentrations in mg/L. Calculate the mass of activated carbon (in mg) needed for 2 L of water.