Question

Store A sells fabric for $3.00 per yard.

Answer 1

Store A:
 sells fabric for $ 3.00 per yard:
 c (t) = 3t
 The domain restrictions for this case are:
 numbers greater than or equal to zero
 Equivalently:
 t that belongs to [0, infinity)

 Store B:
 sells packages of fabric for $ 3.00 each:
 c (t) = 3t
 The domain restrictions for this case are:
 numbers greater than or equal to zero: [0, infinity)
 integer values only: (1,2,4...n)