Please read the facts carefully and answer all questions that follow.

Kaira wanted to surprise her aunt, who always complained that she had no time to bring her car in for a quick wash because of her busy schedule. Kaira washed her aunt's car after her aunt had gone to bed. The next morning, Kaira's aunt is pleasantly surprised. Her aunt was extremely happy, and promised to take her to Disneyland in Tokyo during her next school holidays. Kaira was very excited, as she never expected that her aunt should give her anything for her surprise services. Kaira went ahead to buy the necessary warm clothes for the trip as the weather was expected to be very cold in Tokyo.

a) What is the nature of Kaira's aunt's promise to take her on the holiday? Citing the principles of the law of contract, explain your answer in brief. Please assume that intention to create legal relation is not an issue, and will be present.

b) Applying the law of contract principles, state whether there is a valid and enforceable contract made between Kaira and her aunt.

c) If her aunt later changed her mind and refused to take Kaira to Tokyo Disneyland, state whether Kaira can sue her aunt for breach of contract.