WASHINGTON (Reuters) - Banks wrote off $3 billion of student loan debt in the first two months of 2013, up more than 36 percent from the year-ago period, as many graduates remain jobless, underemployed or cash-strapped in a slow U.S. economic recovery, an Equifax study showed. The credit reporting agency also said Monday that student lending has grown from last year because more people are going back to school and the cost of higher education has risen. "Continued weakness in labor markets is limiting work options once people graduate or quit their programs, leading to a steady rise in delinquencies...