LOS ANGELES (AP) — Mitsubishi Heavy Industries Ltd. will fight Southern California Edison's allegations of gross negligence in the design and manufacture of steam tubes built for the San Onofre nuclear power plant, which has been permanently shut down due to excessive wear in the tubes. Mitsubishi sent a reply Thursday to a contract dispute filing from Southern California Edison that said the company "grossly failed to appropriately model" conditions in the steam generators it designed and built, leading to the early retirement of the power plant. Edison argues that Mitsubishi is liable for costs that could run into the millions or even billions of dollars. In a statement, Mitsubishi called SCE's contentions "factually incorrect, legally unsound and inappropriate." The company said it will defend itself through a dispute resolution process.