AB is the diameter of a circle of radius 9 cm. PQ is a chord (not a diameter) that intersects AB at M perpendicularly. If AM : BM = 5 : 4, then the length of chord PQ will be:

A

$$5\sqrt{5}$$ cm

B

$$6\sqrt{5}$$ cm

C

$$6\sqrt{3}$$ cm

D

$$8\sqrt{5}$$ cm