Two identical metal balls, each of mass 2.0kg, are initially 0.40m apart and attract each other with force F1. Both masses are then reduced by 20% through machining, and simultaneously the centre-to-centre separation is decreased by 10%.
a. (i) Express the new gravitational force F2 as a multiple of F1.
b. (ii) Hence find the percentage change in the force (give your answer correct to the nearest whole number).