I'm pretty sure it's -4x.
The domain of C = All positive real numbers
The given relationship is:
C = 20W
where:
W represents the weight of the letter in ounces
C represents the cost of sending the letter in cents
The domain of a function is a set of all the input values.
In the function C = 20W, the weights (W) represent the input values.
Since the weight of a letter cannot be negative, it can only contain positive real numbers (Both integers and decimals)
Therefore, the domain of C is a set of all positive real numbers
Learn more here: brainly.com/question/18486099
