Advance financial accounting about unrealised profit

During the year ended 31st December 2009, Grey Ltd has sold goods
to Blue plc for £65,000 (transfer price). The standard gross profit % charged on inter-company sales is 30%.

50% of these goods have since been sold by Blue plc to external customers.

I used to calculate like that , 65000 x 0.3 x 0.5 = 9750
but the marking scheme is given the urp is 13000 . I just wonder how it is calculate or maybe i misunderstand the meaning of transfer price ? Can anyone explain to me step by step . Thank you.