Solution:
If James arrived before Lars then following possibilities exist (left to right in the order of arrival):
1. James, Lars, ______ , _______
2. James, ______ , Lars, _______
3. Jam es,______, _______, Lars (this possibility gives no arrangement)
4. ______ , James, Las,_______
5. ______ , James, _______ , Lars
6. _____ , _______ , James, Lars (this possibility gives no arrangement)
The only arrangements possible for the order of their arrival are:
I. James, Lars, Cliff, Dave (from 1)
II. James, Lars, Dave, Cliff (from 2)
III. James, Cliff, Lars, Dave (from 2)
IV. Cliff, James, Lars, Dave (from 4)
V. Cliff, James, Dave, Lars (from 5)
From the above 5 possible arrangements it is evident that Dave could never be the 2nd friend to arrive.
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