Consider the general supply function:
Qs = 1,000 + 20P - 9PI + 25F
Qs = quantity supplied, P = price of the commodity, PI = price of a key input in the production process, and F = number of firms producing the commodity.
Derive the inverse of the supply function when PI = $480 and F = 60. Then using the inverse supply function, what is the supply price for 40,000 units of the commodity?