The management of a large store wishes to add a fenced-in re…

The management of a large store wishes to add a fenced-in rectangular storage yard of 1200 square feet, using the building as one side of the yard.  The side opposite the store will be constructed of fencing that costs $3 per foot, and the two sides perpendicular to the store will be constructed of pine boards that cost $2 per foot.  Find the x-value that minimizes the cost.