There is an object with mass m on the horizontal plane, which is in a static state and starts to move under the action of constant force F. after time t, the external force is removed, and then after time t, the object just stops. What is the friction force on the object? What is the acceleration of the object before the external force F is removed? Two ask ha, don't copy, I don't understand them

There is an object with mass m on the horizontal plane, which is in a static state and starts to move under the action of constant force F. after time t, the external force is removed, and then after time t, the object just stops. What is the friction force on the object? What is the acceleration of the object before the external force F is removed? Two ask ha, don't copy, I don't understand them

Using momentum theorem for the whole process
Ft-f * (2t) = increment of momentum = 0
Friction f = f / 2
a=(F-f)/m=F/(2m)