Answer :
divide 3945 by 20 to see how many full bags have to be bought then if you need part of a bag you have to buy one extra 193 full bags 3940 pounds and one extra bag for the other 5 pounds
[tex]3945:20=197,25\\ \\bags\ must\ be\ whole,\ so\ the\ chain\ did\ 198\ bags\ ordered.[/tex]