When imaginative scientists first suggested the possibility that one person could speak directly to another over a long distance, few people took them seriously.
【单选题】Donald consumes goods x and y. His utility function is U (x,y) = xy 3 . He is endowed with 43 units of x and 7 units of y. The price of x is 1 and the price of y is 3. Find his net demand for x.