Can anyone care to help me to expain how the f(t) is form into the step function for the graph to be sketch. i dont understand how to form the f(t) equation into the unit-step function. especially the 2nd qns.

* there are 2 separate diffrent question in the pic. left and right.

http://img441.imageshack.us/img441/5319/hevigv4.png