There are three methods for wastewater treatment in an urban area. The methods remove 1.2 , 2.5 , and 4 g/m³ amounts of the pollutants, respectively. The third technology is the best, but because of some limitations in allocating enough area, it cannot be applied to more than 40% of the wastewater being treated. The costs of applying the treatment methods are 6, 4, and 3 dollars/m3. If the discharge of wastewater that should be treated in a day is about 1,200 m3, and at least 1.677 g/m³

pollutant has to be removed, determine the optimal combination of proposed methodologies in order to treat the wastewater of the urban areas.