AviationTire Flight Planning And Flight Monitoring Flight Plans For Vfr Cross-Country Flights Fuel plan Q 4 / 5

(Refer to CAP 697 - figure 2.5)
What will be the endurance if you plan to cruise at FL80, using power set at 23 in HG (or full throttle) @ 2300 RPM

View figure

4.7 hrs
5.3 hrs
6.1 hrs
6.6 hrs