四、美國聯準會(Fed)為提振美國經濟，多次實施貨幣寬鬆政策(quantity easing)以降低利率，請討論此項政策產生的各種效果。(20分)

2. Given sorting problem µ convex hull，which one of the following statements can be derived ?(Choose one) (1) The Lower Bound of convex hull is W(n log n). (2) The Lower Bound of convex hull is W(n). (3) The Lower Bound of Sorting is W(n log n). (4) The Lower Bound of Sorting is W(n). Please explain how to find the lower bound by problem transformation. (20%)