The U.S. EPA has set the maximum permissible level of benzene (C6H6) in drinking water at 5 ppb. Given that benzene has a Henry’s law constant of 0.18 mol L-1 atm-1, what gaseous concentration of benzene (in ppm) in the air above a body of water would result in the maximum permissible aqueous concentration at equilibrium? Assume an atmospheric pressure of 1 atm.