Well the formula for the volume of a rectangular prism is v=whl or volume= width times height timed length, so let's apply what we know to that. Volume=5*4*4 basically is the math equation we are solving, however because the width and length make up the base we must do the length and width first because another version of the formula is B*h which is area of base *height and width *length equals the area of the base so 4*4= 16, 16*5=80 your answer is the third one 80km^3
