- y n ) 2 ] g n 2 ln [ ( x cl - x n ) 2 + ( y cl - y n ) 2 ] , ( 25 ) ??? ln ( p A / g , P ( A / g , P ) ) ??? P n = ?? 4 P n 2 ??? l = 1 L a nl 2 [ ( x cl - x n ) 2 + ( y cl - y n ) 2 ] g n 2 - L P n . ( 26 ) Variations, modifications, and other implementations of what is may be employed without departing from the spirit and the scope of the invention.