※ Our check while writing this explanation could not fully confirm the published answer; scoring follows IPA's official key.
×Incorrectア
This is likely too small an amount, counting only part of the fee-incurring unmarked equipment. Because not all fee-incurring items among the disposed equipment are summed, it falls short of the total. Since the fee table is not included in the text, the breakdown cannot be pinned down, but it is smaller than the official answer of 7,560 yen and is not the collection total.
×Incorrectイ
Similarly, this is likely an intermediate amount that fails to count part of the fee-incurring equipment. Summing the unmarked equipment without omission should reach the official answer of 7,560 yen; 6,480 yen still falls short and cannot be called the total.
○ウ
正解Under the Act on the Promotion of Effective Utilization of Resources, the PC Recycle Mark shows that the collection and re-resourcing (recycling) fee was prepaid at the time of purchase. Equipment bearing the mark can be collected free of charge at disposal (discharge), without paying an additional collection fee. On the other hand, for equipment without the mark, the person disposing of it (the discharger) bears the collection fee at disposal. In this question only the liquid-crystal-display all-in-one PC bears the mark, so that PC is collected free of charge, and fees arise only for the equipment without the mark. Therefore the total amount associated with collection equals the sum of the collection fees of the unmarked equipment, and the official answer is ウ, 7,560 yen. Note that the fee table and the list of equipment to be disposed of in [the results A investigated], which show each item's fee, are not included in the text, so this 7,560 yen is a value premised on the official key; when displaying it, the original fee table and equipment list must be shown alongside so the derivation can be followed.
×Incorrectエ
A typical mistake in this question. This is likely an amount that misunderstands the meaning of the PC Recycle Mark and even adds in the collection fee of the marked liquid-crystal-display all-in-one PC. Marked equipment has its recycling fee prepaid at purchase and is collected free of charge, so adding that portion is wrong and overestimates the total.
ここがポイント
The PC Recycle Mark shows that the recycling fee was prepaid at purchase, and marked equipment is collected free of charge at disposal (discharge). Unmarked equipment has its collection fee paid by the discharger (Act on the Promotion of Effective Utilization of Resources / PC recycling).
The total collection fee is obtained by summing only the fees of the equipment that incurs a fee burden (i.e., unmarked equipment). The key point is not to add the fees of marked equipment.