If u (t) = 1 for t >= 0 and u (t) = 0 for t < 0, determine the Laplace transform of [u (t) – u (t – a)].

• A. 1/s(1+e(-as))
• B. 1/s(1-e(-as))
• C. 1/s(1+eas)
• D. 1/s(1-eas)