The data for feed consumption and weight gain of our four farm animals labelled P,Q,R and S are shown below.

Use the data to answer this question correctly 

P: 50kg feed consumed and 20kg weight gained.

Q: 90kg feed consumed and 30kg weight gained.

R: 100kg feed consumed and 25kg weight gained.

S: 150kg feed consumed and 30kg weight gained.

The feed conversion efficiency of the poorest weight gainer is?