实验室常用锌块和稀硫酸反应制取氢气，若用6.5克锌和稀硫酸完全反应。则：

（1）可制取多少克氢气？

（2）理论上需要质量分数为19.6﹪的稀硫酸溶液多少克？

Astride entered into a contract with Bild Ltd to construct a wall around the garden of a house she had just purchased. The wall was to be three metres high to block out a view of a rubbish tip. The wall was due to be finished in May and Astride entered into another contract with Chris to landscape the garden starting on 1 June.Bild Ltd finished the wall on 25 May. However when Astride came to examine it for the first time she found that it was only 2·50 metres high and that the rubbish tip was still visible from the top of her garden.On 1 June, Chris informed Astride that he was too busy to landscape her garden and that she would have to get someone else to do it. The only person available, however, will charge Astride ￡500 more than Chris had agreed for doing the work.Required:Analyse the scenario from the perspective of the law of contract, advising Astride:

(a) Whether she can require Bild Ltd to reconstruct the garden wall in order to make it the agreed height, and if not, what alternative action is available to her. (5 marks)