Applied Technology, Inc. $($ATI$)$ produces bicycle frames using two grades of fiberglass material $($standard and professional$).$ Each grade has a different percentage composition of fiberglass, carbon fiber, and Kevlar. The company must use $30$ yards of material per frame and must meet a contract that requires at least $20\%$ carbon fiber and no more than $10\%$ Kevlar in the final mix. The two grades cost different amounts per yard. Formulate a linear program to determine how many yards of each grade to use to minimize total cost, and state the decision variables and constraints.