Riana had a window-shopping in an antique shop. She was then attracted to a vase at the price of RM150. She wished to buy the vase and brought it to the cashier for payment. Unfortunately, by the time she was about to pay, she found out that her wallet was not in her handbag. Riana tried to cancel her purchase but the cashier alleged that Riana was already bound to the contract and therefore was liable to pay for it.

Advise Riana.