Let f(t) = √² - 4. a) Find all values of t for which f(t) is a real number. te (-inf, 4]U[4, inf) Write this answer in interval notation. b) When f(t) = 4, te 2sqrt2, -2sqrt2 Write this answer in set notation, e.g. if t = A, B, C, then te{ A, B, C}. Write elements in ascending order. Note: You can earn partial credit on this problem.