The figures are invented. A firm with market power faces this demand and cost data per day. Outputs of 1, 2, 3, 4 and 5 units sell at prices of $50, $45, $40, $35 and $30. Total cost at outputs 0 to 5 is $30, $55, $75, $100, $130 and $165. (i) Calculate the marginal revenue of the 4th unit. [1] (ii) Calculate average cost at an output of 3 units. [1] (iii) Using marginal cost and marginal revenue, find the profit-maximising output. [1] (iv) Calculate the profit at that output. [1]

HL Paper 3-style calculation (standalone practice; not an IB question).