A local coffee shop charges $4 for a cup of coffee and sell 30 cups per day. They determine that every time they decrease the price of a cup by $0.20 they sell 3 more cups of coffee
per day. What should they charge for a cup of coffee to maximize their profits?

The answer would be $68.04

Idon't see any graph, however the graph of the function : f(x) = x²-2x+3 is a parabola: 1) open upward (since a> 0)2) it intersects y-axis in 3 (y=3)3) its axis of symmetry is x = +1 ( -b/2a)4) it's minimum is y = -2, so its vertex is (1,-2)5) it doesn't intersect the x-axis since discriminant < 0