Personal Pension tax relief

The new rules for stakeholder pensions are now in force and these changes require each individual to adopt a basis year for earnings. This sets earnings at this level for five years (or until altered). Take this situation, a 42 year old individual has basis year (1999-2000) net relevant earnings of, say £50,000. During 2000-2001 actual NRE are only £40,000.

How much tax relief is available at 40%?
Is it based on £50,000 or £40,000? i.e. if maximum pension payments have been made of £7,800 net(£10,000 gross) what repayment would be generated?

Andrew M Stevens