Answer and Explanation:
1. Marta cannot avoid the contract on the basis of a mistake of buying the house because she was supposed to inspect the house she was buying
2. Marta cannot sue Chelene for fraudulent misrepresentation because Chelene was not aware of the condition of the house. The elements in fraudulent misrepresentation are lacking : no intention to deceive, no misrepresentation of material facts
3. It would be Chelene's duty to reveal that there is defect in the house and if not the court would see this as misresprentation.
4. There was no undue influence from Chelene in selling the house and so Marta and Janis even she was alive cannot revoke the contract on this basis