Jack and John are having a Sumo wrestling match. Jack weighs 500
N and John weighs 900 N. John is pushing Jack so that he is sliding
backwards. The coefficient of dynamic friction between Jack’s feet
and the ground is 0.5. If John is applying a horizontal 300 N
force on Jack, what is the magnitude of the force that Jack is
applying to John?
A: 50 N
B: 250 N
C: 300 N
D: 450 N