Could you please answer this question in details and clear writing? Thanks

10. Sweet Delights Co. is considering a marketing policy for its brand of chocolates. Two mutually exclusive advertising strategy changes are under consideration. The cash flows associated with each are as follows. The cost of capital for Sweet Delights is 10%. Strategy Year 0 4 -80 -40 +40 +20 +40 +20 +40 +20 +20 +20 a. Which of the two strategies would you prefer if neither decision can be repeated (ie, all future strategies/ decisions are expected to have zero NPVs)? b. Which of the two strategies would you prefer if each strategy can be repeated as often as possible