Easy math question, many points!

At the electronics store you have a coupon for 20% off up to 2 cds you buy for cds with the original cost of $10.99 each the sales tax is 5% what is the total cost of your purchase

Use your knowledge of the binary number system to write each binary number as a decimal number. a) 1001 base 2= base 10 b) 1101 base 2 = base 10

What is the answer to this problem? ignore the work. what is the correct answer?