Please explain the question to me.

A builder owns three cranes, particulars of which are stated on the right. As at 31 December Year 5 these are reported on the balance sheet at R99 000. The cranes are depreciated at 20% per annum, using the straight-line method and calculating depreciation for the months of use. Crane "B" was sold on 30 June Year 6. Crane Acquired on Cost "A" 1. 4. Year 1 R60 000 "B" 1. 7. Year 3 R40 000 1.10. Year 5 R80 000 The depreciation for Year 6 would be Select one: a. R36 000 b. R23 000 c. R19 800 d. R32 000 x The correct answer is: R23 000