Consider the following statements as regards SAW filter

1. The centre frequency is determined by the pitch of IDT comb shaped electrodes
2. The response can be modified shaping the overlap of comb electrodes
3. The response is maximum when acoustic wave has its wavelength equal to pitch
4. When a number of identical electrodes are arranged at the same pitch, the frequency characteristics of the filter is expressed by (sin x)/x

Which of the above statements are correct?