We have to calculate the salary for one day. Normally, the number of days in a month is taken as 26. If you divide the salary by 26, the one-day salary can be calculated. Then multiply by 30. For example, salary/26*30.
In your case, you have five days working. In such cases, the number of working hours is extended beyond the normal eight hours of working. But the weekly hours remain the same, i.e., it may be 48 hours, equivalent to 6 days of working. Therefore, the basis of calculation should be the same.