γ_ld=+3 · γ_lM=+9 · γ_dM=+15 · T=5.0 · λ=1.0  ·  Unequal target areas (A_l=20, A_d=40) with vacancy nucleation let a medium cavity open, lined by light cells; dark–dark contact grows as dark cells aggregate while heterotypic l–d contact falls (Fig 28; a delicate case).