Answer:
1. 12
2. the prism with a length of 7 1/2 will have a shorter width, with a width of 6
Perimeter is a continuous line forming the boundary of a closed geometrical figure. perimeter of a pentagon = AB+BC+CD+DE+EA (that is 5 sided figure)
so my plan is easy but effective, calculate all those distances using those coordinates with the aid of distance formular. then you add those distances algebraically .
