Well i found this question in my tutorial:

f(t) = 5[H(t-3) - H(t-11)], find the fourier transform.

Ans: (-10/w)(sin w)exp(-2iw)

i am totally blur on how to even start. I tried the general method of fourier transform but got no closer to the answer.

integrate from 3 to 5 for 5.exp(-iwt)

Couldn't find any table with Fourier transform for H(t-a).

All help are appreciated.