Application of Derivatives

A is a point on the circle with radius 8 and centre at 0 . A particle P is moving on the circumference of the circle starting from A. M is the foot of the perpendicular from P on OA and ∠POM=θ. When OM=4 and ‌

dθ

dt

=6 radians ∕ sec, then the rate of change of PM is (in units ∕ sec )