The total cost, c, in dollars, of b bottles of water is c = 1.1b. what is the constant of proportionality?

For the answer to the question above, the constant is called the coefficient of proportionality orproportionality constant. If one variable is always the product of the other and a constant, the two are said to be directly proportional. x and y are directly proportional if the ratio yx is constant.
 the answer is 1.1