easy friction problems

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24:49

16:32

12:51

14:13

4:03

32:33

32:03

27:22

34:55

54:30

2:47:19

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17:51

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33:57

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30:59

24:07

12:52

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25:14

15:16

20:35

15:07

20:57

59:26

33:18

14:56

9:37

13:00

33:22

13:37

19:06

19:01

56:13

11:47

12:57

13:26

1:22

22:04

27:50

15:08

4:45

5:51

16:43

15:24

12:44

11:59

8:38

20:11

7:37

22:57

21:02

26:09