Anchor: When a system involving software is being developed, one or more cost models may be useful.
Entailed: When a system involving software is being developed, there could be more than one model that is useful.
Contradiction: There is a system being developed but there only exists one cost model.
Contradiction: a man is doing the hula
Contradiction: Three men wearing colored costumes take to the streets.
Contradiction: I had hundreds of yards of both curtains and wallpaper at my command.
Contradiction: A woman is checking out a soccer ad.