The finance charge may be computed from the effective date of the insurance coverage, provided that the company shall pay the premium due the insurer, either:
(a) Within 30 days from the effective date of the insurance coverage; or
(b) Within 30 days after the receipt by the company of a proper premium finance agreement; or
(c) Within 15 days after the company has mailed to the insured, notice of a revised finance agreement pursuant to Section 18606 whichever is later.
If the conditions of subdivision (a), (b), or (c) are not met the finance charge shall be computed from the date the proceeds of the loan are forwarded to the insurer. In the event the company receives a proper premium finance agreement later than 60 days from the effective date of the policy financed, a proportioned adjustment of the finance charge shall be made after such 60-day period.