The following four stocks will be used to answer the following questions:

Name of company	# of shares	Price @ time t	Price @ time t+1
Michelangelo	200	10	13
Leonardo	1	15	10
Raphael	100	20	22
Donatello	50	25	23

a. Compute a price-weighted index by adding the stocks prices at time t and time t + 1. What is the percentage change in the index?

b. Compute a value-weighted index by adding the market values of the stocks at time t and time t + 1 What is the percentage change in the index?

c. Why is there a difference between your answers to parts a and b?