Exchange Rate Type upon PO/PR

Hi Experts,

Is there a config to default exchange rate type upon PO/PR creation? I was told that by default it will read type 'M' and I'll be the happiest man if it can link to type 'M'.

In my case, it reads from other type i.e. '2004'. Thus, I was wondering how does it reads and is it based on configuration? Thanks in advance.