Find the total mass of the rectangular box [ 0 , 1 ] × [ 0 , 2 ] × [ 0 , 3 ] {\displaystyle \displaystyle [0,1]\times [0,2]\times [0,3]} (that is, the box defined by the inequalities 0 ≤ x ≤ 1 , 0 ≤ y ≤ 2 , 0 ≤ z ≤ 3 {\displaystyle \displaystyle 0\leq x\leq 1,0\leq y\leq 2,0\leq z\leq 3} ), with density function h ( x , y , z ) = x {\displaystyle \displaystyle h(x,y,z)=x} .