Due that the velocity is constant that means that friction force is equal to the force exert by you, otherwise the refrigerator will accelerate or decelerate and in both cases velocity will not be constant.
So then the friction force between refrigerator and floor is 150 Newtons.
The photon can be absorbed and the energy of the photon is exactly equal to the energy-level difference between the ground state and the level d.
yes she is very safe inside