Find out the time by studying the following pictorial graph.

Calculating time at Prime Meridian (0°) —

• The longitudinal difference: 40° - 0° = 40°
• For 1° longitudinal difference time difference is 4 minutes.
• So, for 40° longitudinal difference, the time difference is 40° x 4 = 160 minutes or 2 hours 40 minutes.
• Since the Prime Meridian (0°) is situated to the east of 40° west longitude, the local time at Prime Meridian (0°) will be: (12 a.m. + 2 hours 40 minutes) = 2:40 a.m.

Calculating time at 50° East longitude or City A —

• The longitudinal difference: 50° - 0° = 50°
• For 1° longitudinal difference time difference is 4 minutes.
• So, for 50° longitudinal difference, the time difference is 50° x 4 = 200 minutes or 3 hours 20 minutes.
• Since the 50° East longitude or City A is situated to the east of Prime Meridian (0°), the local time at City A will be: (2:40 a.m. + 3 hours 20 minutes) = 6 a.m.