Buyer exercises an option to buy a house in August and closes in September. The first seasonal rains pour down a week after closing, and the roof leaks badly. Buyer spends $10,000 on roof repairs. (a) Is the seller liable at common law, assuming he is not a merchant builder or developer, to deliver the house in a habitable condition? (b) Is the seller liable in a disclosure state if he said nothing about the roof leaking in the disclosure statement because he didn't know it would leak? (c) If the seller had known all along that the roof was leaky, and the buyer can prove it, would an 'as is' clause have exonerated the seller? (d) Would the seller be liable if he had promised the buyer he would have the roof repaired before closing, four days before the closing the seller had paid a roofer to fix the leak, and has a receipt to prove it?