why is the answer A?

3. Temasek's financial year end is 30 April. The company depreciates vehicles using the straight line method. On 1 June 2016, Temasek bought a van for $42,000, with an estimated useful life of 5 years and zero residual value. If Temasek sells the van for $20,000 in 31 January 2019, what will be Temasek's gain or loss on disposal? (A) gain of $400. (B) loss of $22,400. (C) loss of $400. (D) gain of $22,000