Revocation refers to the right of a buyer to revoke his acceptance of a lot or commercial unit whose non-conformity substantially impairs its value to him if he has accepted it (a) on the reasonable assumption that its non-conformity would be cured and it has not been seasonably cured, or (b) without discovery of such non-conformity if his acceptance was reasonably induced either by the difficulty of discovery before acceptance or by the seller’s assurances.