WASHINGTON, D.C. (AP).- A nonprofit group that raises money for the National Mall is looking for ideas to overhaul three parts of “America’s front yard” that have been overused and neglected for years. The Trust for the National Mall on Thursday started seeking proposals from architects and designers who will compete to make the mall one of the world’s best parks. Competitors must follow the National Park Service’s plan for the mall developed over four years and signed in November by Interior Secretary Ken Salazar. At the time, he gave the mall a “C” grade for its dead grass, stagnant water and sinking seawalls along its waterways. Such competitions have been integral with the mall’s evolution, from Robert Mills’ white obelisk design for the Washington Monument to Maya Lin’s concept for the Vietnam Veterans Memorial. Bob Vogel, the mall’s new superintendent, said organizers were looking to the “transformat