A construction company wants to make a contract with a subdivision developer by making regular and premium units. In a month, the construction company has 10,000 hollow blocks and 1500 hardiflex materials. A regular unit needs 100 hollow blocks and 30 hardiflex materials while a premium unit needs 500 hollow blocks and 50 hardiflex materials. For each unit of regular and premium units, the company will earn PhP 15, 000 and PhP 25,000 pesos, respectively. If the construction company wants that the premium units are at least 20% of the regular units, then how many of each unit should they have a contract with in a month so that they have maximum earnings?

a. Formulate a linear program for the given problem. b. Graph the constraints manually and determine the intersection points. c. Find the optimal solution to the problem. Conclude properly.