How does a change in the price of a product cause both a substitution effect and an income effect? Does the law of diminishing marginal utility hold true in every situation? Is it possible to think of goods for which consuming additional units, at least initially, will result in increasing marginal utility? Does the fact that the last unit of a person’s income spent on different products and services should give the same marginal utility imply that people should not save at all? Briefly explain.