help me solve this law questions

(a) Francis, aged 17 , was preparing to take his ICA examinations. He agreed to pay Osei, a tutor, GH\$200.00 for private tuition, and ordered textbooks to the value of GHC100.00 from his friend Eric. Francis then changed his mind and told Osei and Eric that he would not require either the tuition or the books. Osei has prepared notes especially for Francis, and Eric has bought the books from the institute. Advise Osei and Eric. (b) Mr. and Mrs. Gyamfi, husband and wife from Ghana visited Los Angeles for a vacation. Mr. Gyamfi left the wife behind on health grounds. He promised to pay her GHS100 a month as maintenance. Mr. Gyamfi could not fulfilled his promise and later the marriage ended in divorce. The wife is contemplating suing for the monthly allowance and has consulted you for advice. Advice Mrs Gyamfi. QUESTION 11 (a)What is meant by the maxim "consideration must be sufficient but it need not be adequate"? Provide relevant examples and case laws to illustrate your answer. (b)To what extent does the Contract Act, 1960 (Act 25) modify the principles of consideration