I really need some help with questions 3 and 4. If you could please explain how you got the answer I would greatly appreciate it! Thank you!

3. (4 pts.) A city charges its water utility customers as follows. Water Usage (thousands of gallons) Rate (dollars/thousand gallons) 7 or less $10 more than 7 $20 For instance, the charge is $140-7x10+3.5x20 for a customer using 10,500 gallons. (a) Write a piecewise function for the monthly charge of using x C dollars thousand gallons of water. 180 160 140 120 100 80 60 40 20 -2 0 2 4 6 8 10 12 14 x gallons (thousands) (b) Sketch a graph of this function on the grid to the right. 4. (6pts) A Company selling a new flavored water has begun an advertising campaign. Its monthly sales are given by the function S(x) = -x + 40x + 500. Here S represents monthly sales in thousands of dollars) x months after the advertising campaign began. (a) Convert S to vertex form by completing the square. Show your work. Lovato 0 (b) What are the coordinates of the vertex? Explain their meaning in the context of the problem. (c) Assume the formula for S is valid only for the first 45 months. So, the domain for S is 0 SXS 45 months. What is the range for S? Write your answer in the interval notation. Show your work (or explain). Range