Green Co. incurs a cost of $15 per pound to produce Product X, which it sells for $26 per pound. The company can further process Product X to produce Product Y. Product Y would sell for $30 per pound and would require an additional cost of $10 per pound to be produced. The differential revenue of producing Product Y is _____.

a.$4 per pound

b.$5 per pound

c.$26 per pound

d.$30 per pound