elizabeth M. suburbs makes $200 a week at her summer job and spends her entire weekly income on running shoes and designer jeans, because these are the only two items that provide utility to her. Furthermore, Elizabeth insists that for every pair of jeans she buys, she must also buy a pair of shoes (without the shoes, the new jeans are worthless). Therefore, she buys the same number of shoes and jeans in any given week.
A. If jeans cost $20 and shoes cost $20, how many will Elizabeth buy of each?
B. Suppose that the pair of jeans rises to $30 a pair. How many shoes and jeans will she buy?