Why taking the best value first fails

• A

  It takes both 5 kg items for 50, which is also the best

• B

  It takes the 6 kg item for 30, which is the best available

• C

  It takes the 6 kg item for 30; the best is the two 5 kg items for 50

• D

  It fills the bag exactly either way, so both give 50