Refer to figures.
1. Find the Groundspeed and flight time from Tharby to Buckland:

• Set wind direction 120°T under the True Index.
• Mark wind velocity 10 kt up from centre dot.
• Set True Course 224°T under the True Index.
• Slide wind velocity mark to TAS 100 kt.
• Ground speed 103 kt reads under the centre dot.
• Flight time: Distance / GS = 16 NM / 103 kt = 0.155 hr = 9 min

2. Find the Groundspeed and flight time from Buckland to Cotby:

• Set wind direction 120°T under the True Index.
• Mark wind velocity 10 kt up from centre dot.
• Set True Course 003°T under the True Index.
• Slide wind velocity mark to TAS 100 kt.
• Ground speed 104 kt reads under the centre dot.
• Flight time: Distance / GS = 57 NM / 104 kt = 0.548 hr = 33 min

3. Calculate ETA overhead Cotby:

• Total Flight time: 9 min + 33 min = 42 min
• ETA at Cotby: 13:30 UTC + 00:42 = 14:12 UTC