The formula for the Area of a Rectangle is
[tex]\text{Area}=\text{L}\times W[/tex]where L is the length and W is the width of the rectangle
From the given problem :
L = 12 feet
W = 4 feet
And the area will be :
[tex]\begin{gathered} A=12\times4 \\ =48 \end{gathered}[/tex]The answer is 48 ft^2