When the box is moving ,it experiences a friction force of 20 n to the left , or toward the mover . what force does the mover need to applying order to keep the box moving to the right at 1 m/s?

Force = mass * acceleration
F = ma

Force = 20 Newtons
Mass = ?
Acceleration = 1 m/s

Here, we don't need to find the mass. Which is why this is such a tricky question. 

Instead, we need to find the force. 

Of course, we know already that force doesn't necessarily require a direction. 

F = 20 N

The force needed would be 20 Newtons, as said. 

therefore, the efficiency is: