Help! I need gelp solving!

Find a) any critical values and b) any relative extrema, f(x)=x2 - 4x+8 a) Select the correct choice below and, if necessary, fill in the answer box within your choice. O A. The critical value(s) of the function is/are (Use a comma to separate answers as needed.) O B. The function has no critical values. b) Select the correct choice below and, if necessary, fill in the answer box(es) within your choice. O A. The relative minimum point(s) is/are and the relative maximum point(s) is/are (Simplify your answers. Type ordered pairs, using integers or fractions. Use a comma to separate answers as needed.) OB. The relative minimum point(s) is/are and there are no relative maximum points. (Simplify your answer. Type an ordered pair, using integers or fractions. Use a comma to separate answers as needed.) OC. The relative maximum point(s) is/are and there are no relative minimum points. (Simplify your answer. Type an ordered pair, using integers or fractions. Use a comma to separate answers as needed.) D. There are no relative minimum points and there are no relative maximum points