Ting, aged 17, an international student studying Commercial Law at RMIT, was running low on money. Ting takes singing and guitar lessons outside of formal studies. Ting hopes to become a professional backup singer and musician for a band in the near future.

Ting sees a new red "Eastrock 39 inch Full Size Electric Guitar Kit" advertised for sale online for $1000 at Billen's Music Pty Ltd. The store promotes a buy- now- pay -later option if a deposit is left. When Ting visits the store to purchase the guitar the manager of Billen's Music store realises that the guitar was incorrectly advertised. The manager indicates that the price for the guitar kit is $1500. Ting was disappointed but offered to take the guitar kit for $1250 since she had travelled such a long way to the store. The manager accepts Ting's offer of $1250. Ting then enters an agreement with the store by leaving her old guitar as a $200 deposit. The manager allows Ting to take the new guitar kit home as the buy now pay later option.

On the way home from the music store Ting was attacked and the guitar was stolen. In the attack Ting's arm was broken, so she went to a local doctor for treatment. The treatment cost $400. Ting wants to know her legal position in relation to finalising payment for the guitar and doctor's fees.

Referring ONLY to the Common Law of Contract, advise whether Ting entered a valid contract with Billen's and the Doctor and whether she must complete payment for the guitar and doctor's fees. Use case references to support your arguments.