On 31 December 2017, a new machine with a useful life of 6 years and an estimated residual value of zero was purchased by a business at a cost of $30,000. The amount of depreciation expense charged for the year ended 31 December 2019, using the reducing-balance method at a rate of 30% per annum, is:

a)$6,300

b) $5,000

c) $9,000

d) $1,800.