You have three continuous parametric functions (in the 3D coordinate system), one in the xy-plane, one in the xz-plane, and the other in the yz-plane. Then, you connect coordinates (x,t) with (y,t) with (z,t),..forming a triangle "slice" with points from these three planar functions for any given "t" (same for each point). One specific triangle for each t-value. Then, I integrate these triangles over a t-interval from t=a to t=b. How do I find the value of this integral ? Next, how do I find the volume integrated by these triangles in the t-interval from t=a to t=b ?