Kenny teaches swimming for Kitty and May. Kenny has agreed to teach each of them one lesson (3 hours) per week and the fee for each lesson is $300. On Ist April, he asked Kitty whether he can receive an additional $1,000 if he could help her to achieve 'a good result' in an upcoming swimming competition. Kitty agreed. She didn't get any prize and refuse to pay him the $1,000. On 10th April, after teaching May for 3 hours, Kenny told her that she only had to pay him $200 since it was her birthday (May and Kenny are also good friends). May agreed and paid Kenny $200. Kenny, however, then regretted and demanded her to pay $100 more being the balance. (a) whether Kitty needs to pay the $1,000 to Kenny; and; (8%) (b) whether May needs to pay the $100 to Kenny for the April 10 lesson.(8%)