Using M-15 filter media and the requirement of 60 cfm per person of outdoor air for the case of a designated smoking area for 55 persons, design a filter and air-circulation system allowing the actual outdoor air rate to be reduced to 20 cfm per person. Assume outdoor and recirculated air are mixed before filtering and insignificant amounts of outdoor air contaminants are present. The filter media must have a gravimetric efficiency of 80 percent in the 0-5 x 10-3 mm particle size range. The filter pressure loss should not exceed 0.12 in. wg.