Q1 

Done quite well. In part (b) it was necessary to check c(j) <= 0 for
all 6 values of j (1,..,6). In part (c) a couple marks were lost if it
was
not clear what the c.s. conditions were.

Q2

Done very vell.

Q3

Not marked. I only ensured that it was done.

Q4

Done very well.