Could you help giving me explanations on this problems ?

There are three events in a triathlon: a swim (event 1), a bike (event 2), and a run (event 3). Todd wants to complete a triathlon, but he can only continue to the next event if he successfully completes the event prior. If he fails an event, he stops there. Let F,S,T be the events that Todd completes the first, second and third event respectively. Assume that P(F)=0.9, P(S | F)=0.8, P(T | FnS)=0.7. What is the approximate probability that he completes all three events? a '