Elizabeth is an older woman who lives alone with a cat named Whiskers. She sometimes has trouble getting to the grocery store, especially when the sidewalk is slippery. Elias is an artist who lives two doors away from Elizabeth. This past winter, Elias would drop off a small bag of groceries and cat food outside Elizabeth's door each time it snowed, so she and Whiskers wouldn't go hungry waiting for the sidewalks to be cleared. Elizabeth did not ask Elias to help in this way, but Elizabeth is very grateful for Elias's help. After the last snowfall of the year, Elizabeth thanked Elias for his help and said that she would like to give him $125 as an expression of thanks. Elias didn't want to take Elizabeth's money, but his art sales had been slow and he could use the cash. Thus, Elias agreed to take the $125. Elizabeth, however, never paid Elias. As it turns out, Whiskers is sick and needs an operation. You are Elias' friend - he has come to you for advice.

a. Do Elizabeth and Elias have a contract, yes or no?

b. Identify the legal issue at the centre of this case.

c. Please explain the answer by applying the law to the facts of this case.