Temperatures: 20%, 17%, 14%, … form an A.P. with common difference ( -3% ).
Fourth measurement temperature = ( 20 - 3\times 3 = 11% ).
Assuming current is proportional to the temperature percentage and the initial current 1080 mA corresponds to the first measurement (20%):
[ \frac{1080}{20} = 54 \implies \text{current at 11%} = 11\times 54 = 594,\text{mA}. ]
Alternatively, the successive currents themselves form an A.P.: [ 1080,; 1080\times\frac{17}{20}=918,; 918\times\frac{14}{17}=756,; 756\times\frac{11}{14}=594. ]
Answer: 594 mA