Lantern substitution and new symplectic 4-manifolds with b₂ ⁺ = 3

Motivated by the construction of H. Endo and Y. Gurtas, changing a positive relator in Dehn twist generators of the mapping class group by using lantern substitutions, we show that 4-manifold K3#2CP² equipped with the genus two Lefschetz fibration can be rationally blown down along six disjoint copies of the configuration C₂. We compute the Seiberg-Witten invariants of the resulting symplectic 4-manifold, and show that it is symplectically minimal. Using our example, we also construct an infinite family of pairwise non-diffeomorphic irreducible symplectic and non-symplectic 4-manifolds homeomorphic to M = 3CP²#(19 - k)CP² for 1 ≤ k ≤ 4.