Find the function f (t) in terms of unit step function in the graph shown below.

• A. 4t [u (t) – u (t + 5)]
• B. 4t [u (t) + u (t + 5)]
• C. 4t [u (t) – u (t – 5)]
• D. 4t [u (t) + u (t – 5)]