A normal magic square of order n is a square array having n horizontal rows and n vertical rows, in which the n2 entries are precisely the positive integers 1 through n2, such that the sum of the entries along any row, column, or diagonal is equal to the same value, kn.
(a) Show that, in a normal magic square of order 3, the entry in row 2 and column 2 must be 5.
(b) Show that, in a normal magic square of order 3, the entry in any of the four corner positions cannot be 1.