Consider the sides of the rectangles be $\"\"$ and $\"\"$ .

Area of the rectangle is $\"\"$ .

Area of the rectangle is $\"\"$ ft².

Hence $\"\"$

$\"\"$ .

The rectangle field is divide into two parts then perimeter is $\"\"$ .

$\"\"$

The cost of the fence is minimum when its first derivative becomes zero.

Apply derivative on each side with respect to $\"\"$ .

$\"\"$

Equate $\"\"$ to zero.

$\"\"$

Substitute $\"\"$ in $\"\"$ .

$\"\"$

Therefore the cost of fence will be reduced when dimension is $\"\"$ ft by $\"\"$ ft.

The cost of fence will be reduced when dimension is $\"\"$ ft by $\"\"$ ft.