Fill in the gap:

(a). If good X is cheaper than good Y, and a consumer decides to consume more of good X and less of good Y, the effect is known as ---- effect.

(b). If the price of a good goes down and, a consumer decides to consume more of that good, the effect is known as -------- effect.

(c). If a consumer's income goes up and the consumer consumes less of good M, good M is known as ------ good.

(d). A consumer's budget line assumes that the consumer spends ----- of their income.