In dichloromethane, CH2Cl2, ( = 1.60 D) the dispersion force contribution to the intermolecular attractive forces is

Question:

In dichloromethane, CH2Cl2, (µ = 1.60 D) the dispersion force contribution to the intermolecular attractive forces is about five times larger than the dipole-dipole contribution. Compared to CH2Cl2, would you expect the relative importance of the dipole-dipole contribution to increase or decrease
(a) In dibromomethane (µ = 1.43 D),
(b) In difluoromethane (µ = 1.93 D)? Explain.