SELECT
 COUNT(q1.*) AS Expr1,
 q2.Expr2,
 q1.MNAME
FROM Problem q1
JOIN MONTH m1 ON DATEPART(m, q1.Date_Assigned) = m1.M_No AND MONTH(q1.Date_Assigned) = MONTH(q1.Date_Closed)

LEFT JOIN

(
    SELECT COUNT(*) AS Expr2, m2.MNAME
    FROM MONTH m2
    JOIN Problem p2 ON m2.M_No = DATEPART(m, p2.Date_Closed)
    WHERE (YEAR(p2.Date_Assigned) = '2012')
          AND (p2.TYPE = 'sr')
          AND (p2.STATUS = 'Resolved')
          AND (MONTH(p2.Date_Assigned) < MONTH(p2.Date_Closed))
        GROUP BY m2.M_No, m2.MNAME, p2.TYPE, p2.STATUS

) AS q2 ON m1.MNAME = q2.MName

WHERE (YEAR(q1.Date_Assigned) = '2012')

 AND (q1.TYPE = 'sr') AND (q1.STATUS = 'Resolved')

GROUP BY m1.M_No, m1.MNAME, q1.TYPE, q1.STATUS

ORDER BY m1.M_No, m1.MNAME, q1.TYPE