Sludge, Inc., entered into a contract with XYZ, Inc., whereby Sludge was to build a building for XYZ in Detroit, Michigan, at the price of $1 million. Sludge was incorporated in Ohio; its principal place of business was in Chicago, Illinois. XYZ is a Delaware corporation with its home office in New York. The contract was negotiated primarily in Chicago but became effective when it was signed at XYZ’s home office. There was a dispute concerning the agreement, and XYZ sued Sludge in a federal district court in Ohio. Which state law would govern the dispute if the court follows

(1) The lex fori approach,

(2) The lex loci contractus approach, or

(3) The lex loci solutionis approach?