Hi,
Note that the "British pound" isn't a unit of weight (lb.) but rather a unit of currency. By weight, the lb. is the same (British or American), though Brits usually use grams or kilograms rather than pounds, for weight.
The currency conversion from the British pound (£) is roughly equal to $1.22
Answer:
Over the last two centuries the dipole strength has been decreasing at a rate of about 6.3% per century. At this rate of decrease, the field would be negligible in about 1600 years. However, this strength is about average for the last 7 thousand years, and the current rate of change is not unusual.
Persian Gulf is the answer
