Receipt Accrual - Month End - Foreign Currency

We have scenario where a Purchase Order is raised in a non-functional currency.

The Purchase Order has the Exchange rate when the PO was raised and once PO is approved, the exchange rate date cannot be updated.

If the PO is in our case for delivery of services over 2-3 years, the FX Rate can move consdierably between PO generation/approval and receipt and invoice.

Question :-

Does the month-end accrual process use the Exchange rate

of the original PO

or the receipting line

I believe this dependent on purchasing options

There is also a delay between receipting and invoicing which can be a substantial time.