A concrete manufacture is concerned about how many units of two types of concrete elements should be produced during the next time period to maximize profit. Each concrete element of type I generates a profit of $60, while each element of type II generates of a profit of $40. Two and three units of raw materials are needed to produce one concrete element of type I and II, respectively. Also, four and two units of time are required to produce one concrete element of type I and II, respectively. If 100 units of raw materials and 120 units of time are available, how many units of each type of concrete element should be produced to maximize profit and satisfy all constraints? Try using the following three methods to answer this question (1) Based on your subjective judgment/guess, specify a solution you believe to be a good solution (1 point); (2) Develop a Excel model (1 point), and then (3) Use Excel Solver for the solution (1 point); and (3) also try to use GA (Premium Solver) for the solution (1 point). Finally, compare the results from these three methods (subjective judgment, Solver, and GA) and describe your observations and conclusions (1 point).