sp1 = 24000

for the first comp. he gained 20% profit which is equal to 1/5

cp1 : sp1

denominator: denominator+nominator

5 : 6

5*4000=20000:6*4000=24000

sp2 = 24000

for the first comp. he loss 20% which is equal to 1/5

cp2 : sp2

denominator: denominator-nominator

5 : 4

5*6000=30000:4*6000=24000

total cost price cp = cp1+cp2 = 20000+30000 = 50000

total selling price sp = sp1+sp2 = 24000+24000 = 48000

total loss = 50000-48000 = 2000

hence cp : sp

50000:48000

25:24

1/25*100 = 4%

he got loss of 4% answer.