I had a spare hour today and i tried the question and, Hmm, I'm either using the wrong formula's or there is an error with my triple integration.
What I am trying to do is:

So basically, find the volume of the cone (1/3 * pi * r^2 * h) which is in m^3
Which is 43633231.3m^3
Now we need to use tripple integration to find the Gravitational attraction of the x component. So you draw a 3D cone, pick a source point, or origin, whichever you call it and set up the axis there.
I'm using this formula
where G = gravitational constant, x = height of cone, crillic is the radius of the cone, and l = distance from source, and then density (g) is just density (which is p in your notes)
However whenever i integrate it and inpt the values, it gives me an insanely large number. Which leads me to believe that i am using the wrong formula. Gravitational attraction is in N right, if so then no way can this mass have a gravitational attraction of 10^6 N.
Also in case you were wondering, the density of the water makes no difference to anything, it cancels itself out when taking the vertical component.
Let me know if I am using the right approach, as I do not know the maths involved with geophysics.