At-shirt department store cost 7.50.the total cost in dollar of a t-shirt is givien by the function c(a)=7.5a

Given cost function C(a) = 7.5a, where a is the number of T-shirts.

Let us complete table.

We need to plug a=1,2,3,4 in above function to get the costs to complete the table.

For a =1

C(1)= 7.5(1) = 7.50

For a =2

C(2)= 7.5(2) = 15.00

For a =3

C(3)= 7.5(3) = 22.50

For a = 4

C(4)= 7.5(1) = 30.00

In order to find the common difference we need to find the diffrences of costs 15-7.50 = 7.50

22.50-15.00=7.50.

a represents the number of T-shirts.

Domain of a is the numbers we can take for a.

So, we can take value for a as 0 or greater value.

Therefore, domain for a would be a is gerater than or equal to 0.

answer: a.   one is a factor of every whole number since every number is divisible by itself.