A wholesaler buys a batch of ceiling fans at a 50% markup over the factory's base cost ₹C. He then allows a 20% trade discount to the retailer. The retailer applies a 40% markup on his cost and offers a flat 10% discount to customers on the printed price. If a customer finally pays ₹18,144, what is the original base cost (₹C) of one ceiling fan from the factory?