Whether Civil Code section 1642 applies in a particular case is a question of fact for the trial court. (Brookwood v. Bank of America (1996) 45 Cal.App.4th 1667, 1675.) However, the Court reviews de novo a court's decision whether the language of a contract entitles a party to attorney fees. (Exxess Electronixx v. Heger Realty Corp. (1998) 64 Cal.App.4th 698, 705.) Section 1642 of the Civil Code provides: "Several contracts relating to the same matters, between the same parties, and made as parts of substantially one transaction, are to be taken together." "The fundamental goal of contractual interpretation is to give effect to the mutual intention of the parties." (Bank of the West v. Superior Court (1992) 2 Cal.4th 1254, 1264.) The Court held that we give "great weight" to the "contemporaneous construction of the contract by the parties themselves prior to the time controversy over its meaning arose." (Lix v. Edwards (1978) 82 Cal.App.3d 573, 579; see also Civ. Code, 1636 ["A contract must be so interpreted as to give effect to the mutual intention of the parties as it existed at the time of contracting, so far as the same is ascertainable and lawful."]) If the intention of the parties to a contract is "doubtful," the rules governing interpretation of contracts, including Civil Code section 1642, "are to be applied." (See Civ. Code, 1637.)