When 150 joules of work is done on a system by an external force of 15 newtons in 20. seconds, the total energy of that system increases by. (1) 1.5 × 102 J
(2) 2.0 × 102 J
(3) 3.0 × 102 J
(4) 2.3 × 103 J

Please include an explanation

Currents in dc transmission lines can be 100 a or higher. some people are concerned that the electromagnetic fields from such lines near their homes could pose health dangers. for a line that has current 150 a and a height of 8.0 m above the ground, what magnetic field does the line produce at ground level? express your answer in teslas and as a percentage of the earth’s magnetic field, which is 0.50 g. is this value cause for worry?