Answer:

500₹ for 125 watts

1 watt=(500/125) ₹=4₹

as per no. of watts for 400 watts total money is 400*4=1600 and for 500 watts 2000₹ respectively

an extra charge is added that is x₹

so, 1600+x:2000+x=21:25

21(2000+x) =25(1600+x)

42000+21x=40000+25x

2000=4x

500=x

extra charge that is fixed for service is ₹500

hope u understood any doubt msgg

sorry bro ykskskxifjrifodkskc