Answer: i dont know how exact you want it but the answer is 31.4159265359
Step-by-step explanation: you have to double the raduis and multiple buy pie.
Well when you multiply it would most likely be 180
First add the prices of the original books.
2.5+4.95+6=11.45
Find 20% of 11.45
=2.29
Therefore I saved $2.29
