3.22 LO4 Equipment was acquired on 1 July 2012 for $50,000 by HiLite Ltd. Its life was determined as being:

• useful—5 years

• economic—8 years

• physical—10 years.

The estimated residual values at the end of these respective periods are:

• after 5 years, $20,000

• after 8 years, $4,000

• after 10 years, nil.

(a) Over what period should HiLite depreciate the equipment?