Who carries the risk of the exchange rate if the Contractor pays for an item in another currency which is to be paid for by the Employer in the currency of the contract?

Which Party carries the risk of changes in the exchange rate if the Contractor chooses to pay for an item in another currency which is to be paid for by the Employer in the currency of the contract?

If an item is to be paid for by the Employer in the currency of the contract and the Contractor chooses to pay for it, or part of it, in another currency, the Contractor carries the risk of changes in the exchange rate. Payment to the Contractor is not affected.