B using more coal to make electricity
let x represent the number of cats of Steve.
Statcie's cat

You multiply 20,400 by 10 which will equal 204,000
3p-8=13-4p
+4 +4
so now you got 7p-8=13
+8 +8
and now you have 7p=21 and how many times does 7 go in to 21 and you should get p=3 and there you go
The answer is c hope this helps 100% sure did this a long time ago