If the quantity supplied of a commodity Qs (measured in tonnes per week) is a function of its price P (measured in £ per tonne) such that:

Qs = 2*P-8

a) Find the inverse function, in other words generate an equation for P in terms of Qs. (3 marks)

b) Identify the maximum price level P at which the quantity supplied Qs is zero. (2 mark)