Chapter 8.1, Problem 19ES

Exercises 19-20 refer to unions and intersections of relations. Since relations are subsets of Cartesian products, their unions and intersections can be calculated as for any subsets. Given two relations R and S from A to B,
   $R\cup s=\{\left(x,y\right)\in A\times B|\left(x,y\right)\in Ror\left(x,y\right)\in S\}$

   $R\cap s=\{\left(x,y\right)\in A\times B|\left(x,y\right)\in Ror\left(x,y\right)\in S\}$

Let $A=\{2,4\}$ and B= {6,8,10} and define relations R and S from A to B as follows: For every
   $(x,y)\in A\times B,$

   $\begin{array}{l}x\text{}Ry\iff x|y\text{}and\\ xSy\iff y-4=x.\end{array}$

State explicitly which ordered pairs are in $A\times B$ ,
   $R,S,R\cup S,andR\cap S.$