Onehundredantennasareputtingoutidenticalwaves,givenby

E $=0\mathrm{.}02$cos$1$e $-$ vt$2$V$>$m

The waves are brought together at a point. What is the ampli$-$ tude of the resultant when $($a$)$ all waves are in phase $($coherent sources$)$ and $($b$)$ the waves have random phase differences?