Which will fill first?

Look a bit closer guys.
 
1 has open flow to 2 and 3. 3 line is lower than the line to 2. 3 has an open line to six. 2 has an open line to 4. The line to 6 from 3 is slightly lower, from the drawing, than the line fro 2 to 4. 6 will be the first to completely fill. This is assuming moderate flow into 1.
 
Since 6 is blocked at end of tube and 7 is blocked at beginning ..... 3 will fill first.
 
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