FIRST DIVIDE THE FIGURE INTO 4 PARTS
FIGURE 1 ----------- CUBOID(78*10*56)
(PLUS)FIGURE 2 ----------- HALF SOLID CYLINDER BEFORE CUBOID (OF HEIGHT 15 AND DIA=78)
(PLUS)FIGURE 3 ----------- HALF SOLID CYLINDER BACK OF CUBOID (OF HEIGHT 15 AND DIA=78)
(MINUS)FIGURE 4 ----------- HALF SOLID CYLINDER (OF HEIGHT 40 AND DIA=62)
NOTE: since the object is symmetric about X and Y - axis Xc =0 and Yc=0. we need to find only Zc