And see my summary below.
b. Determine whether you would prefer life A or life B to be your life AND state the reasons for your preference. Focus your answer on isolationg whatimportance feature your chosen life possess that is lacking in life unchosen. Consider what conclusions/implications about the nature of happiness are suggested by your preference.

Imagine the life you would describe in c above; or, the most desireable life you can imagine living. Now imagine that life lived in The Experience Machine (chapter 10), not in reality. So, describe the emotions, thoughts and feelings you would want to have over your lifetime, and that all of them are recreated in the experience machine. Answer this question: Would you prefer life in the machine over the life that you are most likely to live in reality (as far as you can estimate)? Explain the reasons for your decision and what this implies about the nature of happiness, and the ultimate goals you set for your life. What is happiness given your position on the thought experiment?

See my summary below.

BRIEF summary of the happiness curve:
The first interesting point Nozick makes is that we care about more than the total amount of happiness in our life. This is clearly shown by considering two lives with the same amount of happiness in them, but where one (A) slopes continuously upward to increasing happiness as time goes on. The other life (B) slopes continuously downward. However, both lives have the same amount of happiness in them. Despite the equal amount of happiness, A seems like a clearly preferable life. Things are always getting better, and we live with the expectation of good things in the future. B has the added pleasures of remembering past happiness, though things continue to decline. Nozick believes that almost everyone would choose A over B if presented with such a choice. Thus, something else other than the mere amount of happiness matters to us, since that is the only basis for our preference. What is the something else? Nozick calls it the 'narrative direction' of happiness, its shapes and contours over a life. We want good experiences structured in a certain way, not just stuffed in a bucket.

BRIEF summary of the experience machine:
The Experience Machine! This is cool, and it shows something important about happiness. Suppose for the sake of argument that we had a machine which completely recreated the nature of real experiences in your mind as you float in a tank. When in the tank you completely believe your experiences are real. Moreover, you can program any range of experiences that you want to; any series of highs and lows, different values, different careers, etc. You could program the experiences to seem very real to life as well, but very positive. From the inside, your life will feel as good as possible. Would you get in for your whole life? Why not? From the inside, nothing could be missing. You can even feel like you're growing, and real and deep, and changing. Again, from the inside, nothing is missing. If you would not get in, then you must care about more than how things feel from the inside. The Experience Machine shows this clearly, although many of us assume that how things feel to you is what determines the quality of your life. Now this seems mistaken, or so Nozick argues.