\( \left.\begin{array}{|l}\begin{array}{r}\text { (a) Find the following side lengths for the net. } \\ A=3 \\ B=8 \mathrm{~cm} \\ C\end{array} \\ D=4 \mathrm{~cm} \\ \text { (b) Use the net to find the surface area of the prism. } \\ \square \mathrm{cm}^{2}\end{array}\right] \).

To find the missing side length \( C \), we can use properties of polygons. If this net is for a rectangular prism, and sides \( A \) and \( D \) are the height and width respectively, then knowing that the area of the base gives us a clearer picture. You can calculate side \( C \) by considering the arrangement of the net and the dimensions of similar sides. To calculate the surface area of the prism, use the formula for the surface area \( SA = 2lw + 2lh + 2wh \) where \( l \) is the length, \( w \) is the width, and \( h \) is the height. This means you'll take the values of sides \( A \), \( B \), \( C \), and \( D \) to derive the total surfaces — don’t forget to consider the area of all six faces!