Instructions: DO NOT USE CALCULATOR. Figures are not drawn to scale. A customer came to a shop and asked the shop manager to give a 20% discount on listed price of a pen. Moreover, for every 10 pens purchased he wanted two pens free of cost. The manager agreed to the customer's demand because he could still make a profit of 20% on cost price. If the cost price of a pen is x, what was the list price of the pen?

Explanation: (B) Let L be the list price of one pen. Customer buys 12 pens (gets 2 free for buying 10) but pays for 10 pens at a discounted price. Total list price of 12 pens = \(12L\). Total discounted price of 10 pens = \(10L \cdot (1 - 0.20) = 8L\). This is the revenue for 12 pens. Cost price of one pen is x. Total cost price of 12 pens = \(12x\). Profit is 20% of cost price, so Revenue = \(12x \cdot (1 + 0.20) = 1.2 \cdot 12x = 14.4x\). Revenue = Discounted Price: \(8L = 14.4x\). \(L = \frac{14.4x}{8} = 1.8x\).