A charging station for a certain model of tablet devices is designed to prolong battery life by charging the first 60 percentage points (charge levels 0 .. 60 %) at full power and the last 40 percentage points (charge levels 60 … 100 %) at 80-percent power. The station charges one device from empty to full battery in 9 hours. It can be assumed that there is no battery consumption during the charging process. How many percentage points (changes akin to 1 % to 2% or 57 % to 58 %) does the charging station charge in one hour?