I figured this out eventually and I am convinced it is right and I hope it is of use to someone out there.It goes riff1,riff2,riff,1,riff2 and so on.
p.s. Please rate this tab

G|9--9--9--9--10
D|-77-77-77-77--       x1
A|--------------
E|--------------

G|8--8--8--8--10
D|-66-66-66-66--       x1
A|--------------
E|--------------

And just repeat as many times as you like!! :)