SQL & PL/SQL

Hi All
I asked this question in my previous post, please bear with me on this as this question is almost same with a slight variation. In my last post i said i wanted the count of weekdays for each month prior to the date the query is run, but now i just want the solution to get the count of weekdays in a month. I have the following query:

SELECT   TO_CHAR (TRUNC (date_read, 'mm'),
                  'MON-YYYY',
                  'nls_date_language=english'
                 ) month_year,
                

         COUNT (CASE
                   WHEN speed_avg <= 45
                   and speed_avg!=0
                   and vol_sum!=0
                   AND lane_type = 'm'
                   AND (hour_read || qtrhr_read) IN
                          ('61', '62', '63', '64', '71', '72', '73', '74', '81', '82', '83',
             '84','153', '154', '161', '162', '163',
             '164', '171', '172', '173', '174', '181', '182')
                      THEN 1
                END
               ) count_rows_less_than_45,
         (  COUNT (CASE
                      WHEN speed_avg <= 45
                      and speed_avg!=0 
                      and vol_sum!=0
                      AND lane_type = 'm'
                      AND (hour_read || qtrhr_read) IN
            ('61', '62', '63', '64', '71', '72', '73', '74', '81', '82', '83',
             '84','153', '154', '161', '162', '163',
             '164', '171', '172', '173', '174', '181', '182')

                         THEN 1
                   END
                  )
          / COUNT (DISTINCT asset_id||direction)
          / 24
         ) count_ratio,
         COUNT (DISTINCT asset_id||direction)
    FROM its_sensor_15min
Where TO_CHAR (date_read, 'fmday') NOT IN ('saturday', 'sunday')
GROUP BY TRUNC (date_read, 'mm')

All i need is count of weekdays so that i can divide the count_ratio in the sql with count of weekdays per each month, in my earlier all the users gave me invaluable ideas and approach user SBH created a function and asked me to call it in my query but for some reason its taking forever ( i have index on the field). Frank greatly assisted me as well, but please if anyone else can find a solution or direct me in a direction it would be great.

Thanks