A shawl requires 1 hour of spinning the yarn, 1 hour of dyeing the yarn, and 1 hour of weaving. An afghan needs 2 hours of spinning the yarn, 1 hour of dyeing the yarn, and 4 hours of weaving. There are at most 16 hours for spinning, at most 12 hours for dyeing, and at most 28 hours for weaving. If each shawl sells for $30 and each afghan for $80, what is maximum revenue? (Let x = the number of shawls and y = the number of afghans)