According to newtons 3rd law, every force has an equal and opposite force, which means that the answers for a and b should be the same.
you might be knowing the equation of F which is
F = G(m1)(m2)/(r^2) ( this formula may be wrong, look it up on google)
G is the universal gravitation constant, just google for the exact value, the value should be something like 6.67E-11
m1 is the mass of an apple
m2 is the mass of an orange
r is the distance between them ( should be squared)
