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   ∪   s = { ( x , y ) ∈   A × B |   ( x , y )   ∈   R   o r ( x , y )   ∈   S }

   R   ∩   s = { ( x , y ) ∈   A × B |   ( x , y )   ∈   R   o r ( x , y )   ∈   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 )   ∈   A × B ,

   x ​   R   y   ⇔   x |   y ​   a n d x   S   y ⇔   y − 4 = x .

State explicitly which ordered pairs are in A × B ,
   R , S , R ∪ S ,     a n d   R ∩ S .