The bridge must be 1 meter long, must span an 80.00 cm long gap, must only weight 200 GRAMS, road bed must be long enough for 2 hot wheel cars to pass thru(7cm) and must have a deflection of less than 2.5cm.

What lightweight material could I use to build this as strong as possible? We are being graded on the ratio of the mass of the bridge to the actual weight it holds. Thanks any help is appreciated.

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