This question has two parts. First, answer Part A. Then, answer Part B. Part A Select the correct choice to complete the sentence. a. Determine whether f(x)=7x2−21x+8 has a maximum or a minimum value. The function has a 1 of 1.. Part B Fill in the blank question. b. Then find and use the x-coordinate of the vertex to determine the maximum or minimum. The x-coordinate of the vertex is The maximum/minimum value is .