Paper 1 May/June 2004 Accounting (9706/12) A Level

William buys radios for $\$ 10$ each and sells them for $\$ 15$ each.
His draft statement of financial position included a value of $\$ 1500$ for inventory.
His method of calculation of inventory was correct.
He then found that 12 radios could only be sold for $\$ 8$ each and 4 radios had been stolen.
By how much should William reduce his inventory valuation?