If for a perfectly competitive firm, price is Rs 7.2, output is 4500 units, average variable costs are Rs 1.2, and average total costs are Rs 4. The firm's profits are equal to
The angle of elevation of the top of a pillar from the foot and the top of a building 20 m high, are 60° and 30° respectively. The height of the pillar is
A shop keeper earns a profit of 12% on selling a book at 10% discount on the printed price. The ratio of cost price to the printed price of the book is