Volume
Volume[reg] gives the volume of the three-dimensional region reg.
Volume[{x1,…,xn},{s,smin,smax},{t,tmin,tmax},{u,umin,umax}] gives the volume of the parametrized region whose Cartesian coordinates xi are functions of s, t, u.
Volume[{x1,…,xn},{s,smin,smax},{t,tmin,tmax},{u,umin,umax},chart] interprets the xi as coordinates in the specified coordinate chart.
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