Answer
A) under the facts given, yes the contract was formed. There was mutual consent, offer and acceptance, and also consideration.
B) it is a simple contract made orally, whereas, a formal contract needs seal and writing.
C) it is an implied in fact contract because, the purchaser used gestures or waiving the hands to show that he needs to buy vase, and the proprietor understood it and smiled implying that Joan can take the vase and she kept the bill to ensure that she made payment. Whereas, express contract required writing or willful expressing of the terms.
Joan, while browsing at a busy flea market, sees a vase she likes. The proprietor is...