The shaded part of the given figure indicates the feasible region. Then the constraints are

If the volume of a tetrahedron whose conterminous edges are $$\vec{\mathrm{a}}+\vec{\mathrm{b}}, \vec{\mathrm{b}}+\vec{\mathrm{c}}, \vec{\mathrm{c}}+\vec{\mathrm{a}}$$ is 24 cubic units, then the volume of parallelopiped whose coterminous edges are $$\vec{\mathrm{a}}, \vec{\mathrm{b}}, \vec{\mathrm{c}}$$ is

The joint equation of the pair of lines through the origin and making an equilateral triangle with the line $$x=3$$ is

If 1 is added to first 10 natural numbers, then variance of the numbers so obtained is