In a regular polygon, the number of diagonals is 'k' times the number of sides. If the interior angle of the polygon is, then the value of k is

a) (3i-i)/2(i-i)
b) 2(3i-i)/(i-i)
c) 2(i-i)/(3i-i)
d) (i-i)/2(3i-i)
where i = pie = 180 degree.