(a) Prime cost method: $30,000 x (1 / 5) = $6,000 first-year deduction.

(b) Diminishing value method: $30,000 x (2 / 5) = $12,000 first-year deduction.

Controlling authority: Division 40 of the Income Tax Assessment Act 1997 (Cth) - the capital allowances (decline in value) rules. The prime cost formula is in section 40-75 and the diminishing value formula (with the 200% rate for assets first held/used on or after 10 May 2006) is in section 40-72.