In a certain region of space, electric field is along the z-direction throughout. The magnitude of electric field is however not constant, but increases uniformly along the positive z-direction at the rate of 10⁵ N C⁻¹m⁻¹. The force experienced by the system having a total dipole moment equal to 10⁻⁸ C m in the negative z-direction is

Consider an electric dipole with −q charge at A and +q charge at B, placed along z-axis, such that its dipole moment is in negative z direction. i.e., Pz = 10⁻⁸ C m
The electric field is along positive direction of z-axis, such that dE/dz = 10⁵ N C⁻¹m⁻¹
From, F = qdE = (q × dz) × dE/dz = p dE/dz
Force experienced by the system in the negative z-direction, F = p × (−dE/dz) = 10⁻⁸ × (−10⁵) = 10⁶N.