If you notice the picture below, the amount of fencing, or perimeter, that will be used will be 3w + 2l
now

solve for "w", to see what critical points you get, and then run a first-derivative test on them, for the minimum
notice the

so. you can pretty much skip that one, though is a valid critical point, the width can't clearly be 0
so.. check the critical points on the other
Answer:
The bags would weigh 27lbs. multiply 4 1/2 and6 and you get 27lbs.
6 times because 6•7=42 so it must be 6 because 7•7=49
Good luck!!
If you work out the equation the answer would be 5 but its not a definite answer.