A jaguar can reach speeds of 100 km/h. Usain Bolts top speed during the 100 m dash

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Question:

A jaguar can reach speeds of 100 km/h. Usain Bolt’s top speed during the 100 m dash was 12.26 m/s. Suppose a hungry jaguar spots Usain and starts running towards him at tops speed. When the jaguar is half a km away, Usain sees it and starts running away from it. It takes Usain 0.8 seconds to reach his top speed (he has a constant acceleration during that time), after which he continues at top speed.

How much time does Usain have before his inevitable demise?