Also, the rice bag is still on the ground, in a static state. ∴ f+N=G meters. Then: n = g m-f = 800 n-500 n = 300 n.
The supporting force n of the rice bag and the pressure F' of the rice bag on the ground are a pair of interacting forces. Pressure f'= n = 300 Newton.
Therefore, c in the option is correct.
So choose C.