Kiran swims in a 90 m long pool. He covers 360 m in two minutes by swimming from one end to the other and back 0 along the same straight path, twice. Find the average speed of Kiran.

A

$$4 ms^{-1}$$

B

$$6 ms^{-1}$$

C

$$3 ms^{-1}$$

D

$$5 ms^{-1}$$