The beginning of the amazing events at Krakatoa in 1883 date to May 20 when there were initial rumblings and venting from the volcano, which had been dormant for about 200 years.
A refinery margin is the revenue associated with refining petroleum, expressed as a value per volume (e.g. $/L), net of the cost of the crude oil input. The simplest refining
Net margin is net profit divided by net revenues, often expressed as a percentage. This number is an indication of how effective a company is at cost control. The higher the net margin is, the more effective the company is at converting revenue into actual profit.