Jacoby Company received an offer from an exporter for $28,000$ units of product at $$18$ per unit. The acceptance of the offer will not affect normal production or domestic sales prices. The following data are available:

Domestic unit sales price $$23$

Unit manufacturing costs:

Variable $11$

Fixed $6$

The differential revenue from the acceptance of the offer is

a$.$ $$1,148,000$

b$.$ $$644,000$

c$.$ $$504,000$

d$.$ $$140,000$