A crocodile is stalking prey located 20 metres further upstream on the opposite bank of a river. Crocodiles travel at different speeds on land and in water. The time taken for the crocodile to reach its prey can be minimised if it swims to a particular point, P, x metres upstream on the other side of the river as shown in the diagram. The time taken, T, measured in tenths of a second, is given by T(x)= 5 √(36 + x2) + 4 (20 - x)
![2303_Crocodiles travel at different speeds.png](https://secure.tutorsglobe.com/CMSImages/2303_Crocodiles%20travel%20at%20different%20speeds.png)
What is the minimum amount of time needed for the crocodile to catch its prey?