When the price of a product​ changes,
a. it only causes an income effect by changing the purchasing power of the consumer.
b. it changes the relative price of the product causing a network effect and at the same time it changes the purchasing power of the buyer causing an income effect as well.
c. it changes the relative price of the product causing a substitution effect and at the same time it changes the purchasing power of the buyer causing an income effect as well.
d. it only causes a substitution effect by changing the relative price of the product?
