Can you show me how can i trace the answer using paper?

Given the suppliers$-$parts $-$projects database, where the supplier supplies parts for projects, what is the resulting output table?

select snumber, sname

from supplier

where not EXISTS

$($select $*$

from part

where not EXISTS

$($select $*$ from spj WHERE

spj$.$snumber $=$ supplier.snumber AND spj$.$pnumber $=$ part.pnumber $))$