$6\mathrm{.}7$ Consider the following portions of two different programs running at the same time on four processors in a symmetric multicore processor $($SMP$).$ Assume that before this code is run, both $x$ and $y$ are $0.$

Core $1$: $x=2$;

Core $2$: $y=2$;

Core $3$: $w=x+y+1$;

Core $4$: $z=x+y$;

$6\mathrm{.}7\mathrm{.}110$