Hi
Good question - the (lack of!) depreciation info for the year for plant and equipment is certainly an unusual feature.
Usually, depreciation figures given in the trial balance are accumulated figures to the start of the year, and we're given separate info in the info below the trial balance about how to work out the depreciation for the current year and we incorporate this into the cost of sales (as you say).
This question doesn't provide any information about how to work out the current year's depreciation for the plant and equipment. So, we have nothing to incorporate into the cost of sales. For the property, we are explicitly given info below the trial balance, so can explicitly include this as you say.
[For the plant and equipment we are, instead, implicitly assuming that this year's depreciation has already been reflected in the information provided, eg the accumulated plant and equipment depreciation already includes this year's figure as does one of the other costs of sale, perhaps the manufacturing costs.]
Hope this helps
Lynn