It's looking touch and go whether the Footsie index will open above 6,000 this morning with City traders suggesting the blue-chip index will open around 16 points higher, just 1 point short of the 6,000 level.Rio Tinto has increased its offer for Riversdale Mining to A$16 a share in cash, securing the backing of management for a deal worth A$3.9bn (£2.5bn). The mining giant admitted earlier this month it had talked to the Sydney-based firm, which has interests in African coal, about a A$15 a share takeover valuing the business at £2.2bn (A$3.5bn).Pharmaceuticals giants AstraZeneca and Abbott have dissolved their collaboration agreement covering the development of Certriad capsules. After the US FDA issued a Complete Response Letter for the Certriad new drug application the two companies decided that the resulting regulatory delay meant development of Certriad is no longer commercially attractive. Outsourcing giant Capita has announced two bolt-on acquisitions. It is buying hotel and meetings bookings firm BSI for £42.5m, and ICT services provider SunGard Public Sector Holdings for £86m.