The question is : four masses shown in figure 12.14 (Knight 12.14) are connected by massless, rigid rods. (see attached fig) A) find the coordinates of the center of mass B) find the moment of inertia about a diagonal mass that passed through B and D so I got part a right by setting the x-y axis at A and using X-bar=(200g(10cm)+200(10))/700g=(40/7)cm=5.7cm Y-Bar=5.7cm I'm unsure how to do part B I can use the parallel axis theorum I=[/cm]+M[d[/2] but I'm unsure how to use the MD^2 part. M i just the sum of all the masses right? D would (√x^2+y^2)^2 which is just x^2 plus y^2. But they're askng for a number for moment of inertia and i dont know which point they are looking at on the diagonal rod. What am i missing here?