Cadence and Harmony are sisters. They are the only two directors of MusicWithMe Ltd, a company that sells personalized musical instruments. The company uses a group of select suppliers for their instruments as they market themselves as only selling top quality, hand-made instruments with a soft, whimsical sound. When they need a new supplier or when they visit a supplier to make an order, it is always Cadence who goes because Harmony, despite her name, is tone-deaf and can't distinguish a well-tuned, carefully crafter instrument from the others. Everyone at MusicWithMe Ltd knows that Harmony is tone-deaf and it was even included in her contract that she is not permitted to order or buy any instruments without Cadence being present. A new supplier, SpringInMyStep Pty Ltd has just popped up and MusicWithMe Ltd is very keen to see what type of instruments they have. They make an appointment with Trevor, the manager of SpringInMyStep Pty Ltd, but on the morning of the appointment Cadence feels unwell and decides to stay home in order not to spread germs around the office. Harmony is not keen to miss the appointment with SpringInMyStep Pty Ltd so she decides to go by herself. Trevor knows that Harmony is a director and he is very attentive and shows Harmony all the instruments. Harmony is very impressed by the quality of the instruments in terms finish and look. The instruments are very unique and limited in supply, so Harmony makes the executive decision to order 100 instruments. She signs a contract with Trevor and returns to the office. The instruments arrive two days later, and while they do look very good, the sound is something completely different. On closer inspection, Cadence and Harmony come to realize that the instruments are purely ornamental, intended to be displayed on walls and shelves but never played. Cadence calls Trevor to tell him that they cannot keep the instruments and that Harmony did not have the authority to purchase them in the first place because she is tone-deaf. Trevor apologies, but says that they have a no return policy and he had no idea that Harmony was tone-deaf.

Cadence and Harmony want to know whether the contract is valid or not under both common law and statute law. Please advise.

*Can the law of Freeman Lockyer v Buckhurst, Hely Hutchinson v Brayhead to be used in this case? If can, can explain and elaborate more to me? Also, can use indoor management rule for the common law?

Appreciate your help, thanks in advance!