U(t) = 0, 0 t<7;U(t) = (t-7)3, t 7;

• A. nThe Laplace transform of U (t) is ___________
• B. ( frac{6e^{-7s}}{s^4} )
• C. ( frac{3e^{-7s}}{s^4} )
• D. ( frac{6e^{-7s}}{s^3} )
• E. ( frac{3e^{-7s}}{s^3} )