We disagree because the clear purpose of that provision is to limit Hedges from "adding together different policy coverages to increase available coverage limits." Nat'l Merit Ins. Co. v. Yost. 101 Wn.App. 236, 241, 3 P.3d 203 (2000); see also Thomas V. Harris, Washington Insurance Law § 39.01, at 39-3 (3d ed. 2010) ("Antistacking provisions are often contained within a UIM policy's 'other insurance' clause.").
¶8 We enforce the policy language as written when it is clear and unambiguous. Nat'l Merit Ins. Co. v. Yost, 101 Wn. App. 236, 239, 3 P.3d 203, review denied, 142 Wn.2d 1011 (2000). A term is ambiguous if it is fairly susceptible to two different but reasonable interpretations by an average insurance purchaser.