A person incurs only voidable contractual duties by entering into a transaction if by reason of mental illness or defect
he is unable to understand in a reasonable manner the nature and consequences of the transaction, or
he is unable to act in a reasonable manner in relation to the transaction and the other party has reason to know of his condition.
Where the contract is made on fair terms and the other party is without knowledge of the mental illness or defect, the power of avoidance under Subsection (1) terminates to the extent that the contract has been so performed in whole or in part or the circumstances have so changed that avoidance would be unjust. In such a case a court may grant relief as justice requires.