Week B1 Laboratory Sample Solutions don't seem to have been released. Here is a list of what has been released:
Tut Questions: 01 02 03 04 05 07 08 09 10
Tut Solutions: 01 02 03 04 05 07 08 09 10
Lab Exercises: 01 02 03 04 05 07 08 09 10 B1 B2
Lab Solutions: 01 02 03 04 05 07 08 09 10