Answer:
Gavin is allowed to revoke if he finds Rod's efforts half-hearted
Step-by-step explanation:
given data
Gavin pay for paint his house = $400
solution
as given Gavin pay Rod for paint his house at $400 but Gavin want to revoke the offer so Either he accepts, or he does not accept the offer.
If he starts to paint the offer, and Gavin doesn't like his work, the offer may be canceled.
so scenario is Gavin is allowed to revoke if he finds Rod's efforts half-hearted