Answer:
The magnitude of the frictional force is 
Explanation:
From the question we are told that
The force exerted on the box is 
Generally for the box to remain at rest then it means that the frictional force is greater than or equal to the force applied to move it i.e

=> 
RADIATION
There are three types of heat transfer or heat propagation; conduction, convection and radiation. Heat transfer is the process by which heat projects externally however, depending on the temperature and pressure. Also called the movement of heat from a low temperatured state which increases as heat progresses.
Conduction is the heat transfer by contact, immediate contact.
Convection is the transfer of heat through air and water.
<span>Radiation is the transfer of heat regardless of the presence of atoms or particles.<span>
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Answer:
yes done first thing tomorrow