M2 OCR moments question

Can someone give me a hand here please? I've found the COM but am unsure what to do next


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Couple of things you could do for part i.

Triangle of forces - note the line of action of three forces in equilibrium goes through a common point.

Or.
Resolve vertically to get the vertical component at A.
Take moments about B to get the horizontal component at A.
Use Pythagoras to combine and get the magnitude.