Section 177 of the Evidence Act, 1975 (NRCD 323) amplifies these principles as follows: “(1) Except as otherwise provided by the rules of equity, terms set forth in a writing intended by the party or parties to the writing as a final expression of intention or agreement with respect to those terms may not be contradicted by evidence of a prior declaration of intention, of a prior agreement or of a contemporaneous oral agreement or declaration of intention, but may be explained or supplemented, (a) by evidence of consistent additional terms unless the Court finds the writing to have been intended also as a complete and exclusive statement of the terms of the intention or agreement, but a will and a registered writing conveying immovable property shall be deemed to be a complete and exclusive statement of the terms of the intention of agreement; and (b) by a course of dealing or usage of trade or by course of performance. (2) Subsection (1) does not preclude the admission of evidence relevant to the interpretation of terms in a writing.”