A young's double-slit experiment is performed with green- blue argon light with =515 nm, the slit separation is 0.4mm . (a) At what angle is

A young's double-slit experiment is performed with green- blue argon light with  λ=515 nm, the slit separation is 0.4mm . 

(a) At what angle is the 2^nd  order located? 

(b) If the slit to screen distance is2.75m, find the distance on the screen between the 2nd order maximum  and central maximum. 

(c) Find the distance on the screen between the 3^rd  order maximum and 2^nd  order maximum.