Carol is Mia's childminder. She minds Mia's house for 6 hours each week and is paid 60. Last week, Mia asked Carol if she would be willing to do some extra work as she is having a party on Saturday evening and needed to mind the baby for the evening. Carol was minding the baby for the evening while Mia was attending guests. It took her an additional 4 hours. Mia was extremely pleased with Carol's help and told her that there would be a bonus in pay next week. When Carol was paid at the end of the week, she was surprised to receive only 20, especially since she had worked 10 hours instead of her usual 6. Mia has now refused to pay her. She says that her promise of payment came after Carol has performed her duty. Does Carol have an enforceable contract with Mia for the work carried out?