Consider the excluded volume interaction between spherical particles with effective pairwise interaction potential for
U(r)={[infinity] for r ≤ 2R, -kBT₀(2-r/2R) for 2R ≤ r ≤ 4R, 0 for r ≥ 4R}
where kBT₀ is the strength of the attractive potential with T₀ = 100K. Calculate the excluded volume of these particles.