Ashok went to a shop to purchase a total of 71 pens, pencils and sharpeners. The cost of each pen, each pencil and each sharpener are Re. 1, Rs. 2 and Rs. 3 respectively. If the cost of each pen had been Rs. 6 more and the cost of each sharpener had been Re. 1 less, the total worth of his purchase would have been Rs. 92 more. If he bough at least 20. Articles of each, how many pencils did he purchase?