Cantwell associates, a real estate developer, is planning to build a new apartment complex consisting of one-bedroom units and two- and three-bedroom townhouses. a total of 156 units is planned, and the number of family units (two- and three-bedroom townhouses) will equal the number of one-bedroom units. if the number of one-bedroom units will be 3 times the number of three-bedroom units, find how many units of each type will be in the complex.