A short case of Void and Voidable Contract

Mary, a weak but mentally sound 87-year old woman, is in the front garden of her old weatherboard home. Duncan, a big man who was heavily tattooed and wearing leathers, parks his motorbike outside her garden and strikes up a conversation with Mary. He told Mary that: “I am a licensed painter and I could paint the exterior of your house for a good price – $8000”. Mary obviously felt intimidated by Duncan and hastily agreed. The next day Duncan arrived and over the next two days painted her house. During this time Mary discovered from her daughter’s inquiries that had Mary received competitive quotes for the painting work, the going rate for painting her house was about $4000. Her daughter also discovered that Duncan’s registration as a licensed painter had lapsed two weeks ago because he had forgotten to pay the renewal fee. The job is now complete and Duncan has asked Mary for $8000.

Question:

Is Mary contractually obligated to pay Duncan the $8000? Why?

Ans: No, Mary is not contractually obliged to pay Duncan the $8000. In the given case, there are circumstances that make this contract voidable. It is seen that Mary was intimidated by the Duncan presence and immediately agreed the Duncan’s offer. It seems that Mary was under the undue influence (even if Duncan has not such intention) while she concluded the contract because Duncan has represented himself in such a way that has probability to influence the mind of ordinary person and actually affects the person mind leading an old lady, Mary, to enter into the agreement.
In addition, it is also mentioned that the Duncan’s has forgot to renew his license fee and had not provided the quotation as well. Further Duncan has quoted the price as $8000 which according to the prevailing rate was $4000. It shows some ill intention (Mens Rea) of Duncan to deceit.
We know that any contract done under the coercion, under influence, fraud and deceit is not automatically void but is consider voidable at the option