Some pens were packed into 2 boxes. At first, there were 120 pens in Box P and 30% of them were red pens. There were 80 pens in Box Q and 40% of them were green pens. After some pens were transferred from Box Q to Box P, 40% of the pens in Box P and 60% of the pens in Group Q were red pens. What was the percentage decrease in the number of pens in Box Q after the transfer?
