A particle of mass m and energy E scatters off a repulsive potential V(r)=V0(a/r)2 for r<a and V=0 for r>a, where V0>0.
(a) Show that only the s-wave contributes in the low-energy limit ka≪1.
(b) Find the s-wave phase shift δ0 for this potential.
(c) Find the total cross section in the low-energy limit.