How long a bailout bottle lasts at depth. The usable pressure is the fill pressure, less the absolute pressure at depth and the 10 bar the regulator needs.
The formula: Usable pressure = fill - (absolute + 10). Change any box and the full working updates. For study only, never for dive planning.
The IMCA ADS, BDS and LST papers ask this as a four-option question, with a calculator on screen. A free account gives you 15 practice questions for each exam, each with the worked answer and the document it comes from.