I think it’s A.) it explains why the universe is made up of matter
1.igneous rocks are formed when magma or lava cools and hardens
2. the cooling rate of the rock
Answer:
1.40 N
Explanation:
The magnitude of the frictional force is given by:

where
is the coefficient of friction
N is the magnitude of the normal reaction
The coefficient of friction for this problem is
. The magnitude of the normal reaction is equal to the combined weight of the boy and the sled, because the surface is horizontal, so

Therefore, the frictional force is

read it carefuly you will understand why?????