2004年，自治区党委、人民政府决定在乌鲁木齐、库尔勒等八个城市开办区内初中班，重点招收农牧民子女及其他家庭贫困的学生．某市2004年9月招收区内初中班学生50名，并计划在2006年9月招生结束后，使区内初中班三年招生总人数达到450名．若该市区内初中班招生人数平均每年比上年的增长率相同，求这个增长率．

Kabelo is sitting with a group of his friends outside a restaurant by the river. He says that he will give P2,000 to anyone who can swim across the river. Kabelo puts the amount of the money on the table to show the seriousness of his challenge. Modisa is not with Kabelo’s group but is sitting at the table next to Kabelo. He hears the promise but does not say anything. Suddenly a child falls into the water from the other side of the river. Modisa dives into the water and begins to swim to her rescue. As Modisa is approaching the child, Kabelo shouts out: ‘Don’t think you are going to get my P2,000 because I am withdrawing the offer!’ Modisa nonetheless rescues the child and climbs out onto the other side of the harbour.Required:Explain whether Modisa can claim the P2,000 from Kabelo under the law of contract. (10 marks)