Please show any working out. Any help will be apprciated.

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My tennis coach analyses every game that I play. She has found that I get the first serve in about 70% of the time. When I get the first serve in, I win the point about 80% of the time. If I miss the first serve, the second serve goes in about 90% of the time. When this happens, I win the point about 30% of the time.

a) Find the probability that I win a point when I am serving

b) If I win a point while serving, what is the probability that I only

needed one serve?