I'm having some problems with calculus and this is really my last resort... if someone can help me its due in 3 hours...

A fence is to be built to enclose a rectangular area of 270 square feet. The fence along three sides is to be made of material that costs 6 dollars per foot, and the material for the fourth side costs 12 dollars per foot. Find the length and width (with ) of the enclosure that is most economical to construct.

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A parcel delivery service will deliver a package only if the length plus the girth (distance around) does not exceed 100 inches. Find the maximum volume of a rectangular box with square ends that satisfies the delivery company's requirements.