In the supply-and-demand diagram of the market for peanut butter, the equilibrium point has moved up and to the right. What could have caused this?

	a.	a fall in the price of peanuts
	b.	a rise in the price of peanuts
	c.	a rise in income, assuming that peanut butter is an inferior good
	d.	a shift in preferences toward peanut butter
	e.	none of the above