(a) As to property, casualty and surety insurance the insurer shall maintain an unearned premium reserve on all policies in force.
(b) Except as provided in § 1107 of this title as to marine and transportation risks, the unearned premium shall be equal to the unearned portion of gross premiums in force (after deduction of applicable reinsurance in solvent insurers) computed on an annual, monthly or more frequently pro rata basis.