14 We approached our assessment of the taxpayer's loss associated with Metronet's execution of its business overhead activities in a manner similar to that used to calculate the loss associated with Metronet's operation and maintenance activities. The principal differences were:
■ We assumed that Metronet's payment of its bid costs, an item in its overheads, was made using debt rather than revenue. We therefore deducted this item from this part of our calculation.
■ We drew information about the performance of an efficient and economic company from the report produced by the Arbiter specifically on the subject of Metronet's business overhead activities.
15 We calculated that the taxpayer's loss from Metronet's inefficient execution of its business overhead activities was between £47 million and £100 million (2007 prices) (Figure 16).