dear friend,
1) 12* 31000/31
2) 12 * basic salary/31 and calculate other allowances for 12 days separately in the same procedure
3) 31000/31 you will get one day emoluments and multiply it with 12
4) In some organisations they did not allow other allowances for less than 15 days and these monetary benefits have to be looked into for calculative purpose.
This is the simple procedure to be followed..