De or het leasingovereenkomst?

The correct Dutch article is:

de leasingovereenkomst

How to use leasingovereenkomst

the leasingovereenkomstde leasingovereenkomst
this leasingovereenkomstdeze leasingovereenkomst
that leasingovereenkomstdie leasingovereenkomst
our leasingovereenkomstonze leasingovereenkomst
your leasingovereenkomstjouw leasingovereenkomst
every leasingovereenkomstelke leasingovereenkomst
which leasingovereenkomst?welke leasingovereenkomst?
a big leasingovereenkomst / the big leasingovereenkomsteen grote leasingovereenkomst, de grote leasingovereenkomst