What is wrong with the rule that firms should invoice their customers in hard currencies?

What will be an ideal response?

Invoicing in hard currencies forces the customer to assess the probability distribution of future exchange rates between the customer's currency and the hard currency. If the MNC can do this better or assess it more rationally, then the MNC can increase sales to those who would otherwise not purchase the product. Invoicing in hard currencies also shifts the foreign exchange risk to the customer who may be less sophisticated and less able to manage the risk.