If the following vertices form a parallelogram, find the values of the unknown variables.
 
\(A = (\)8, \(r)\), \(B = (\)26, 4\()\), \(C = (\)74, 38\()\) and \(D = (s\), 38\()\).
 
Figure 13.png
 
\(r =\)
 
\(s =\)