At a container terminal, $168$ containers arrive per hour by truck. The length of a container can be $6,12$ or $14$ meters. From past experience, it is known that $38\%$ of the arriving containers have a length of $6$ meters. Another $40\%$ have a length of $12$ meters and the remaining containers are $14$ meters long. Every incoming container is first checked for damage by an employee. The time to check a container depends on the length of the container and follows a normal distribution. The mean time for checking a container equals $2\mathrm{.}2$ minutes per container plus $1\mathrm{.}9$ seconds per meter length of the container. So a $6$ meter long container requires $143\mathrm{.}4$ seconds for checking. Checking time has a standard deviation of $15$ seconds, regardless of container length.

There are $10$ employees working in parallel to check containers for damage. After checking, containers must be transported to the stack $($the storage area$).$ There are $73$ transport vehicles available each of which transports $7$ containers at a time. It takes $0\mathrm{.}9$ minutes per container to load the transport vehicle. Transport starts when $7$ containers are loaded onto the vehicle. The travel time from the checking area to the stack is $14\mathrm{.}6$ minutes. At the stack the transport vehicle is unloaded, which can be done $18\%$ faster than loading. The return trip of the vehicle is one minute faster, because the vehicle is now empty. The workload is spread evenly over the vehicles.

What is the utilisation of the transport vehicles $($expressed as a number between $0$ and $1)?$