As no available data is given for calculation, we use a hypothetical situation.
Mr A loans $30000 from a company with a flat interest of $6000 (including fees and taxes) for a period of 36 months.
The actual monthly payment for his loan will be:
(Principal+Interest)/number of months
I.e. Total Repayable Amount= $30000+6000=$36000
Monthly Payment for 36 months = $36000/36 = $1000
In cases where the interest is in rates, an approximate formula will be used depending on continuous or discrete compounding.