I am new to Sage, and I couldn't find an answer to two question in the documentation. First, how do I get sage to plot a parametric curve in 3 dimensions, and then fill in the area between the curve and the xy-plane (i.e., I want sage to drop down a "sheet" from the curve to the xy-plane)? Similarly, how do I get Sage to plot a function in 3 dimensions (say, $f(x,y)=x^2y+10)$), and tell sage to fill in the volume under the graph between the function and the xy-plane? So for the function $f$ just mentioned, I would like the volume under the curve filled in over the rectangle $1 \leq x \leq 3$, $0 \leq y \leq 5$. How do I do that? Thanks!