If f(x) =kx3-9x2+9x+3 is monotonically increasing in each interval, thenA) kB) k＜=3C) k＞3D) k＞=3

find f’(x) for monotonically increasing f’(x)>0 (equal to as well but at descrete points)
3kx²-18x+9>0
so
3k>0 as well 18²-4(3k)(9)<0
k>0 and k>3
so final answer k>3 (equal to as well)