Distance from departure point to PET =

DH/O+H

 

D=1100, H=(440-80)=360, O= (440+80)=520

 

(1100x360)/(360+520) = 450nm

 

450nm at a GS of 520 means that Time = Dist/Speed = (450/520) = 0.865hrs = 51.9 mins.