Jon is always willing to trade one can of Coke for one can of Sprite, or one

Question:

Jon is always willing to trade one can of Coke for one can of Sprite, or one can of Sprite for one can of Coke.
a. What can you say about Jon’s marginal rate of substitution?
b. Draw a set of indifference curves for Jon.
c. Draw two budget lines with different slopes and illustrate the satisfaction-maximizing choice. What conclusion can you draw?