One of the subprime market’s largest players, Washington Mutual, says it is ready to make a push for more business, now that it is planning to unload its sizable portfolio of government-insured and fixed-rate conventional mortgages. “This enhances our ability to focus on higher margin products such as option ARMs, home-equity, Alt A and subprime loans,” said Kerry Killinger, WaMu chairman and CEO, explaining the company’s decision to sell $140.00 billion in mortgage servicing