What is the area of a cross section that is parallel to face abcd ? enter your answer in the box. cm²

To solve this problem you must apply the proccedure shown below:
 1. The problem asks for the area of a cross section that is parallel to face ABCD. As is parallel to that face, you have can calculate its area as following:
 A=12 cm x 6 cm
 2. Therefore, the result is:
 A=72 cm²
 The answer is: The area of a cross section that is parallel to face ABCD is 72 cm².

Ithink if im not mistaking b is -3 but im not a 100% sude