Concrete Weight Calculation for Umbrella

I need a quick but reliable calculation that tells me exactly how much concrete ballast a freestanding PVC umbrella will require to remain stable in everyday use and in moderate wind. The umbrella stands about 3 m tall, its square canopy spans between 4 m across, and the entire unit will not be fixed to the ground—so all stability has to come from the base weight alone.

Please work out:
• The minimum concrete mass needed to resist overturning and uplift, using standard safety factors.
• Your assumptions on wind speed, coefficient of drag for a square canopy, and any load combinations you apply.
• A short explanation of the formulas you choose (e.g., moment balance, uplift checks).
• Final recommended base dimensions that accommodate the calculated weight.

A concise PDF or spreadsheet showing the step-by-step math, followed by a plain-language summary, is perfect.