A speculative developer is considering purchasing a site for the construction of 40 detached estate houses. The selling price of the houses is GHS 455,000 each. The cost of the land, inclusive of legal charges, is GHS 1,050,000. The developer requires a profit of 16% of the Gross Development Value (GDV). What is the allowable amount for building costs? Assume legal, agents, and advertising fees to be 3% of GDV.