Ruth and peter have been doing business together for a while.Ruth has a coffee shop in melbourne CBD, and peter owns a factory that produces ground coffee with different flavours.peter has been supplying ground coffee for Ruth for the past four years.For every order, they usually sign a contract. However, recently, as peter got very busy with his business, he adds and modifies term of contract verbally.Ruth is worried about the new trend of modifying terms of contracts verbally. Explain the implications of the "parole evidence rule" on construction of a contract.