Mortgage rates inched lower Tuesday as stocks plummeted on news of the Treasury plan to assist banks and boost lending. Treasury Secretary Timothy Geithner detailed a plan to create a Public-Private Investment Fund with $500 billion seed money to buy distressed securities. The Treasury will also work with the Federal Reserve to provide up to $1 trillion in new consumer and business loans. Markets remained volatile as investors attempted to analyze the plans. Meanwhile, the Senate resumed debate over the proposed $800 billion stimulus package. Concerns over the growing cost of the various government-funded programs pushed Treasury yields higher.