In Maryland Casualty Co. v. Nationwide Mutual Ins. Co. (2000) 81 Cal.App.4th 1082, a homeowners association sued a general contractor alleging negligence by both the contractor and its subcontractors. The general contractor was an additional insured under the subcontractors' liability policies. The general contractor's insurers sued the subcontractors' insurers for failing to pay defense costs for the general contractor. The court held that all of the policies, both those of the general contractor and those of the subcontractors, provided primary rather than excess coverage to the general contractor. Therefore, there was no equitable basis for making the subcontractors' insurers pay all of the general contractor's defense costs, and equitable subrogation did not apply. (Maryland Casualty, supra, 81 Cal.App.4th at p. 1090.) Indeed, it would have been wholly inequitable to make the subcontractors' insurers pay all of the costs, since their policies only obligated them to cover the general contractor for vicarious liability on claims arising from the subcontractors' negligence, not for liability based on the general contractor's own negligence. (Id., at p. 1092.) The appropriate remedy was equitable contribution, to apportion the costs among the insurers based on policy limits, time on the risk, and other factors. ( Id., at p. 1094.)In Maryland Casualty Co. v. Nationwide Mutual Ins. Co. (2000) the Court noted: "While there is no single required method of apportionment, the ultimate goal of equitable contribution must be 'to accomplish substantial justice by equalizing the common burden shared by coinsurers, and to prevent one insurer from profiting at the expense of others.' Consistent with this objective, courts have developed several methods to quantify the insurers' respective risks and achieve an equitable apportionment of loss, including methods based on policy limits, time on the risk, policy limits multiplied by time on the risk, equal shares, and other factors." (Maryland Casualty Co. v. Nationwide Mutual Ins. Co., supra, 81 Cal.App.4th at p. 1094.)