The distance d between a fixed spring and the floor is a linear function of the weight w attached to the bottom of the spring. The bottom of the spring is 18 inches from the floor when the weight is 3 pounds, and 10 inches from the floor when the weight is 5 pounds.
(A) Find a linear equation that expresses d in terms of w.
(B) Find the distance from the bottom of the spring to the floor if no weight is attached.
(C) Find the smallest weight that will make the bottom of the spring touch the floor. (Ignore the height of the weight.)