If Ohner's spouse disapproves the design and Ohner refuses to allow Planner to proceed with the work, is evidence of the oral agreement admissible in Planner's action against Ohner for breach of contract?
Yes, because the evidence shows that the writing was intended to take effect only if the approval occurred 
No, because the parol evidence rule bars evidence of a prior oral agreement even if the latter is consistent with the terms of a partial integration. 
No, because the prior oral agreement contradicted the writing by making the parties' duties conditional.
Yes, because the oral agreement required approval by a third party. 