The distance between the midponts of two metal balls.P and Q,respectively of masses 55 kg and 70 kg is 80 cm

Question

calculate the gravitational force that P exerts on Q
answer
F=Gm1m2/r^2
F=(6,67x10^-11)(55kg)(70kg)/(80cm)
F=4.01x10^-11..... Is it correct is correct
(b)give only the magnitude of the force that Q exerts on P
(c)if Q Is now replaced by a ball that 1/2 its original mass and the distance between the balls is doubled.determine the New force.