City sources predict the FTSE 100 will open down 23 points from yesterday's close of 5,767, tracking US stocks lower ahead of US non-farm payrolls data for April. Bloomberg has estimated an increase of 160,000, while Goldman Sachs reckons on 125,000. Nationalised lender Royal Bank of Scotland (RBS) is to repay the final tranche of notes issued under the government's Credit Guarantee Scheme (CGS) next week, after posting a profit of more than a billion pounds in the first quarter of 2012. Excluding own credit adjustments, pre-tax profit totalled £1,052m. Own credit adjustments, which reflect the increasing price of debt issued by RBS and therefore the assumed cost of buying it back, warranted a pre-tax charge of £2,456m, leaving a statutory pre-tax loss of £1,404m and an attributable loss of £1,524m.Power systems group Rolls-Royce didn't give much away in its first-quarter interim management statement on Friday, but reassured that trading since the start of the year has been consistent with previous guidance. For the year ending December 31st 2012, the group continues to expect "good growth" in underlying revenue and profit with cash flow around break-even as it invests in future growth.Oil giant Tullow has revealed disappointing results from the Teak-4A appraisal well in the West Cape Three Points Block, offshore Ghana. In a short statement, the group said that Teak-4A, in which it is a 26.396% parter, was drilled by operator Kosmos Energy and was drilled to a total depth of 2,850m to target the stratigraphic extension of the Teak discovery area. The well was said to have encountered "thin, non-commercial reservoirs" and is, in turn, being plugged and abandoned.