To answer the question about the total surface area of the giant model of a magnet that needs to be painted, we would need to know the dimensions of the magnet (height and width) in addition to the depth, which is given as 3 feet.
Assuming the magnet has the shape of a rectangular prism or a similar geometrical shape (for instance, two rectangular prisms combined), we can calculate the surface area using the formula:
\[ \text{Surface Area} = 2lw + 2lh + 2wh \]
Where:
- \( l \) = length
- \( w \) = width
- \( h \) = height
Without the specific dimensions of the magnet, I cannot definitively calculate the surface area and provide the correct answer.
If you can provide the height and width of the magnet, I can assist you further in determining the total surface area. Alternatively, if you know that the answer is one of the provided options, please share more information about the shape or typical dimensions used in similar exhibits, and I can help justify the solution.