1. A zip wire is shown as the dashed line $AC$ in the diagram.

The zip wire is supported by two vertical posts $AB$ and $CD$ standing on horizontal ground.

$CD=2.6m$         $BD=12m$

The zip wire makes an angle $x$ with the horizontal, as shown in the diagram.
The design of the zip wire requires the angle $x$ to be at least 5°

Work out the least possible height of the post $AB$
Give your answer correct to 3 significant figures.