Answer: Here it is
1) The range is y . This is true.
2) The domain is all real numbers. This is true.
3) The y-intercept is 4.5. This is False. The y-intercept is 7.
4) There is no X-intercept. This is true.
5) The rate of change is $4.5 per mug. This is true.
C(m) = 4.50m + 7 is a linear function, and the slope of a linear function represents the rate of change (or the unit rate of change) which is 4.5 dollars per mug. The y-intercept represents the cost when no mugs are ordered which is 7 dollars. As the domain is all real numbers this means that Marta can order any number of mugs. And as the range is y this means that the minimum cost for any order will be 11.5 dollars.
And as there is no X-intercept, this means that the function never crosses the x-axis, this means that the function can never have a y value of zero, which confirms that it doesn't have an X-intercept.