The effect on resolution of increasing voltage from 28 to

The effect on resolution of increasing voltage from 28 to 120 kV.
(a) What is the expected ratio of migration times (t120 kV/t28 kV) in the two experiments? Measure the migration times for peak 1 and find the observed ratio.
(b) What is the expected ratio of plates (N120 kV/N28 kV) in the two experiments?
(c) What is the expected ratio of bandwidths (σ120 kV/σ28 kV)?
(d) What is the physical reason why increasing voltage decreases bandwidth and increases resolution?