The buyers are back in the Washington area home market, according to a market trends report released Tuesday by MRIS (the local multiple listing service) and real estate research firm Delta Associates. Sales volume and prices rose in the first three months of this year in the regional market, the report said. Sales volume was up 9.2% from a year earlier; the average price, at $357,983, was up 4.9%. The strongest price gains occurred in some areas hit hard by the foreclosure crisis: Loudoun and Prince William counties. Compared with a year ago, average prices in Prince William rose 26%, and in Loudoun, they rose 11.9%.