A*J = J*A = K*J
"Definition 2.1 A graph r with adjacency matrix A = A(r) is called regular if
there exists a natural number k such that AJ = JA = kJ. The number k is called valency of r."
An Adjacency Matrix, Order and Valency are investigated. The solution is detailed and well presented. The response received a rating of "5/5" from the student who originally posted the question.