(a)  In Codelfa Construction v State Rail Authority of NSW the court decided that the contract was not frustrated because, despite the changed circumstances, it was still possible to build the tunnel and complete the contract.

(b)  In Codelfa Construction v State Rail Authority of NSW the court decided that the contract was frustrated even though, in the changed circumstances, it was still possible to build the tunnel and complete the contract.

(c)   In Codelfa Construction v State Rail Authority of NSW the court decided that the contract was frustrated because, in the changed circumstances, it was impossible to build the tunnel and complete the contract.