Show that intensity is given by i =im (cosb)^2 ((sinx)/x)^2 where b=((pie*d*sino)/labda) and x=((pie*a*sino)/labda)

Try c ? that’s what i got

What formula  this one  (x_/

Velocity=total displacement/timefrom house to store is 500 from store to neighbor is 200 therefore total displacement=500+200=700metrestherefore,700metres/910seconds=0.8metres per second