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
Operating margin is the proportion of revenues remaining after paying the costs of operating the business, such as labor costs (wages), raw materials, overhead, depreciation and amortization, selling, general, and administrative expenses, advertising, etc.