Of the three window types, Rectangular, von Hann and Blackman, if they are all used to design the same type of digital FIR filter with the same number of samples in the impulse response

(a) Which one yields the narrowest transition from passband to stopband?

(b) Which one yields the greatest stopband attenuation?

What is a disadvantage of finite-difference digital-filter design using forward differences? Generally, in order to design a digital filter with a certain passband gain, transition bandwidth and stopband attenuation, which type of digital filter accomplishes the design goal with fewer multiplications and additions, IIR or FIR?