Sam decided he was ready to sell his classic sports car. On May 1 and in the following order, he telephoned Bob, Carla, Dan, and Edna, each of whom had earlier expressed interest in buying the car. He was unable to make actual contact with any of them, so he left the following message on each one’s telephone answering machine: “I’m ready to sell my car, which I know you’ve expressed interest in. The price is $10,000. My offer is good until the end of today, May 1. If you’re still interested, call me back by the end of today so I’ll know for sure.”

Bob, Carla, and Dan each called back at a time when Sam was out running errands. They each left a message on Sam’s telephone answering machine.

Bob’s message said, “The price is pretty high, so I’ll have to think about it.”

Carla’s message said, “I think the price is too high, but I’d be willing to pay you $9,000.”

Dan’s message said, “OK, I’ll pay your price but only if you’ll let me take the car to my mechanic so he can check it out first.”

Edna, rathim than call Sam back, mailed Sam a letter on May 1 stating, “I got your message, and I accept your offer and will pay $10,000.”

On May 2, Sam died. Mark was appointed as executor for Sam’s estate, and as such had all powers to deal with the estate property. Bob, Carla, Dan, and Edna each said to Mark, “I accepted Sam’s offer on May 1, and, in any event, I will buy the car as is and for Sam’s asking price.” Mark tells them each that their so-called acceptances were not valid and that their power of acceptance has already terminated.

Is Mark correct? Explain fully.