Answer:
Explanatioyour answers look right, but if there has , has to be another answer its a , but your answers are right
The force exerted by the magnetic in terms of the magnetic field is,

Where B is the magnetic fied strength and F is the force.
Thus, if the magnetic A has twice magnetic field strength than the magnet B,
Then,

Thus, the force exerted by the magnet B is,

Thus, the force exerted by the magnet B on magnet A is 50 N.
The force exerted by the magnet A exerts on the magnet B is exactly 100 N as given.
Hence, the option B is the correct answer.
A because the girl in that instant is not moving up or down so
( up forces)=(down forces )
The up forces is the tension of the rope and down forces us mg -the gravitational force on the girl by the earth
The direction of a vector multiplied by a scalar is only affected if the scalar is negative, in which case the vector will now be in the opposite direction. If the scalar is positive, the vector will only change in magnitude