What is the equation of the quadratic graph with a focus of (4, −3) and a directrix of y = −6? (1 point) Select one: a. f(x) = negative one over six times x squared plus four over three times x plus eleven over six b. f(x) = one over six times x squared minus four over three times x minus eleven over six c. f(x) = three fiftieth x squared plus eleven twenty fifth x plus three fifth d. f(x) = two fiftieth x squared plus eleven twenty fifth x plus two fifth