$.$ Johnson Plumbing buys an extended reporting period $($ERP$)$ for its contractors professional liability policy. During the regular policy period, three claims were paid and the aggregate limit of liability was reduced. What happens to the policy's aggregate limit of liability when Johnson buys the ERP?

$($Search Chapter $8)$

a$.$ The aggregate limit of liability is restored.

b$.$ Whatever funds remain from the original limit of liability are added to a new limit of liability on the ERP which is equal to the original aggregate limit of liability.

c$.$ The aggregate limit of liability is usually not restored.

d$.$ The original aggregate limit of liability now applies in full to the ERP.