An AI programmer is optimizing a model's performance using a quadratic cost function \( f(x) = ax^2 + bx + c \). If the vertex of this parabola corresponds to the minimum point at \( x = 3 \) and the cost at the vertex is \(-5\), find the relationship between \( a \) and \( c \) given \( b = -6 \). - Groen Casting