physics
posted by squires .
There are Two boxes on top of each other. The top has a mass of 2.99kg the bottom one has a mass of 7.89 kg. A horizontal force of 39.97 newtons is applied to the left to move them both at an acceleration of 1.42m's^2
Find the minimum coefficient of static friction μt between the blocks such that the 2.99 kg block does not slip under an acceleration of 1.42 m/s2.

Where is the force applied, Top or bottom box?

the force is pulling both boxes to the right