What are the coefficients of 60a+30c

Acollege is planning to construct a rectangular parking lot on land bordered on one side by a highway. the plan is to use 680 feet of fencing to fence off the other three sides. what dimensions should the lot have if the enclosed area is to be a maximum?

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Use the knowledge of x- and y- intercepts to choose the correct graph of the equation 3x+6y=6