A 4.00-kg box sits atop a 10.0-kg box on a horizontal table.The coefficient of kinetic friction between the two boxes and between the lower box and the table is 0.600,while the coefficient of static friction between these same surfaces is 0.800.A horizontal pull to the right is exerted on the lower box,as shown in the figure,and the boxes move together.What is the friction force on the UPPER box? 
Definitions:
Behavior
The actions or reactions of an organism, often in response to its environment, which can be innate or learned.
Turtles
Reptiles with a bony or cartilaginous shell developed from their ribs that acts as a shield.
Ichthyosaurs
Extinct marine reptiles that resembled dolphins and lived during the time of the dinosaurs, known for their large eyes and streamlined bodies.
Pterosaur
An extinct group of flying reptiles that lived during the time of the dinosaurs, not dinosaurs themselves.
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