Which of the following gives an example of a set that is closed under addition.
a) the sum of a perfect square and a perfect square.
b) the sum of a prime number and a prime number.
c) the sum of a negative number and a negative number.
d) none of these are an example of the closure property.

12 pack of pens for $1.09

m packs =  1.09*m = 1.09m

1 composition book = $2.79

n composition books = 2.79*n = 2.79n

Total cost = (1.09m + 2.79n)

Since there is a discount of 5%, the net price would be: 100% - 5% = 95%

Net Cost = 0.95*(1.09m + 2.79n)

Cindy's bill =    $ 0.95*(1.09m + 2.79n)