Ali, Ahmad and Sam shared and bought a Play Station III for RM1500. Each of them took turns to keep it for a week. While it was with Sam, he sold it to James for RM1450 without the knowledge of Ali...

Ali, Ahmad and Sam shared and bought a Play Station III for RM1500. Each of them took turns to keep it for a week. While it was with Sam, he sold it to James for RM1450 without the knowledge of Ali and Ahmad. Now Ali and Ahmad are aware of the sale and want the Play Station III back but James is refusing to return it.
Advise Ali and Ahmad.