The following table shows the number of books sold by a shopkeeper in 6 days of a week:
| Days | Sunday | Monday | Tuesday | Wednesday | Thursday | Friday |
| Number of books sold | 65 | 40 | 30 | 50 | 20 | 70 |
What is the difference between the total number of books sold by the shopkeeper on Sunday, Monday and Thursday, and the total number of books sold on Friday and Wednesday?
1
5
2
4
3
3
4
6