Dont click the link the bot sent you they can hack you
I=PRT
P=8000
R=0.015
T=3
I=8000*0.015*3=360
total amount=8000+360=$8360
The original area of a face would be a^2. Now that you added b to the edge, the new area of each face would be (a+b)^2. To find how much the are increased, subtract a^2 from (a+b)^2.
So the answer is b(2a+b)
The full answer would be 83.454 but you can just say 83 pounds. Both are right