Suppose, for modelling simplicity, that an aircraft's fuel burn rate (i.e. the rate at which it consumes fuel over time) decreases the longer the aircraft flies. This occurs because the aircraft burns fuel relative to the weight it carries. Using fuel means less fuel now required to keep a lighter weight aloft. Suppose that an A380's fuel consumption rate can be described by:

/ =()

whereis the Fuel Tank capacity of the aircraft in litres and $F$ is the amount of fuel already consumed in litres.

A A380's 10 fuel tanks can hold a maximum of320,000L but it does not necessarily start every flight with full tanks (i.e.=320000is not necessarily true). Suppose=1.3. What is the rate of fuel burn when the A380 has flown for 4hours if the A380 began its flight with117580 L in its tanks?