3. [In class, we noted that the consumer will spend all their money if they have in- creasing preferences. Here, we give a calculus-based condition for the consumer to spend all their money, that doesn't assume more is always better. The con- dition is a stronger version of what is sometimes called \"local non-satiation\".] Let :1: e X, and let MU. denote the marginal utility for good i 6 {1,2} at 2:. (a) Suppose some good i has MU. 76 0 (it could be positive or negative), and suppose the consumer is not spending all her money at bundle I (that is p - :r 0 if MU.-