A sailor went to sea, sea, sea to see what he could see, see, see

A sailor in a boat, which is going due east with a speed of $$8 m/s$$, observes that a submarine is heading towards north at a speed of $$12 m/s$$ and sinking at a rate of $$2 m/s$$. The commander of the submarine observes a helicopter ascending at a rate of $$5 m/s$$ and heading towards west at $$4 m/s$$. Find the speed of the helicopter with respect to the boat in $$m/s$$.

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