Depreciation

Question 54 , kaplan exam kit:

Increasingly the international Accounting standard Board is requiring or allowing current cost to be used in many areas of financial reporting .
Drexler acquired an item of plant on 1 October 2002 at a cost of $500,000. It has an expected life of five years ( straight line depreciation ) and an estimated residual value of 10% of its historical cost or current cost as appropriate. As at 30 September 2004, the manufacturing of the plant still makes item of plant and its current price is $600,000.

What is the correct carrying amount to be shown in the statement of financial position Drexler as at 30 September 2004 under historical cost and current cost?

Historical cost Current cost
$320,000 $384,000

Calculation
historical cost annual dep = $90,000 (500,000* 90%)/5 yrs
After 2 yrs CA would be = $320,000(500,000-180000.
Current cost annual dep= $108,000( $600,000*90%)/5yrs
After 2yrs CA would be $384,000( 600,000-216).
My question is this an acceptable way for this calculation .. ? Becaus i am now feeling a bit insecure of Kaplan ways.