(b) The turning point of is at (0, 22). Use this fact to get an equation with a and c in it. Make a the subject and substitute into .
Now substitute this expression for y (and your value of b) into and solve for c. (You will need to use technology to do this).
Substitute your value for b and c (and hence a) into and solve for y. If you need more help please post everything you've done and state exactly where you're stuck.