Select the correct answer.Consider functions f and g.f(x) = x^2+ 7xg(t) = 3x- 1What is the value of (f•g)(x)?A. 9x^2 + 15x – 6B. 3x^2 + 7x - 1C. 3x^2 + 21x + 1D.9x^2 + 21x – 1