Convert from petagram to quartern

Unit Definition (petagram)
The petagram is a metric unit of mass equal to 10E15 grams or 1 gigatonne (one billion metric tons). This unit is used in atmospheric science and other scientific contexts where large masses are considered.

Unit Definition (quartern)
The quartern is a traditional English unit of weight equal to 1/4 stone, 3.5 pounds, or about 1.5876 kilogram.