Calculate the fourier transform of
$$ f(t) = \begin{cases} b & \text{für } a \leq t \leq a+1 \\ 0 & \text{sonst} \end{cases} $$
and write the result in a way, that we clearly see the influence of a.
So...
$$ F(\omega) = \int_{a}^{a+1} b e^{-i \omega t} dt = \frac{b}{-i \omega} (e^{-i \omega (a+1)} - e^{-i \omega a}) = \frac{b}{-i \omega} e^{- i \omega a} (e^{-i \omega} -1 ) $$
but what is the meaning of "the clear influence of a"...?