For the following pairs of goods, would you expect the cross-price elasticity of demand to be positive,

Question:

For the following pairs of goods, would you expect the cross-price elasticity of demand to be positive, negative, or zero? Briefly explain your answer.
a) Red umbrellas and black umbrellas
b) Coca-Cola and Pepsi
c) Grape jelly and peanut butter
d) Chocolate chip cookies and milk
e) Computers and software