A compound machine is a combination of simple machines in which the output of the first part of the machine generates the input to the next part. A certain compound machine consists of three stages (parts) where the first part has an AMA of 6.8 and an IMA of 10.0, the second part has an AMA of 13.8 and an IMA of 16.4 and the third part has an AMA of 7.1 and an IMA of 12.6. What is the overall percent efficiency of this compound machine?