Don't know if this helps but a few ideas might help you

Since due west of port linseed and then due north port linseed we have a right angle triangle with two sides the same length 5.2 and therfore the other two angles will be both 45 degrees as 90+45+45 = 180 and 180-45 will be the other angle, we know the times 10:04 and 10:40 and distance between these two points is x squared = 5.2 squared + 5.2 squared so can get the distance and work out the speed from that, then we know the time from 11:10 to 10:40 and use this same speed to get the length of the side of new triangle.

maybe this will spark you with some fresh ideas how to solve this