Depreciation

Hi sir, plz help. Question: Plant and equipment sold during the year for $15,000 had originally cost $60,000 five years ago. The plant and equipment were depreciated on the straight line basis over six years. Any gain/loss on disposal has been included in overheads. Overheads include the annual depreciation charge of $100,000 for property and $230,000 for plant and equipment. Calculate the gain/loss on disposal. Gain/Loss on disposal= Proceeds- CV Proceeds=15,000 CV= Original amount- accum depreciation =60,000- ???? my issue is the accumulated depreciation...there is not straight line % or any information on depreciation charge for plant and equipment , apart from the comment on annual depreciation charge of $230,000 for plant and equipment.. what am I missing?? plz help! Thanks