To determine the surface area of the glass surfaces, we will determine the area of each rectangle and sum them.
The area of a rectangle is given by the following formula:

Now, the rectangles that compose the total surface area of glass have dimensions:

Therefore, the total area adding up the areas of the rectangles is:

Answer part a:

Now, the area covered by the plastic lid is the area of a rectangle of dimensions

Therefore, the surface area of the plastic surface is:

Answer part b:
