We prove a formula computing the Gromov-Witten invariants of genus zero with three marked points of the resolution of the transversal A3-singularity of the weighted projective space ℙ(1,3,4,4) using the theory of deformations of surfaces with An-singularities. We use this result to check Ruan’s conjecture for the stack ℙ(1,3,4,4).