What is the smallest separation between two slits that will produce a second-order minimum for 800 nm red light? what is the relationship for destructive interference for a double slit? μm

The rocket is fired vertically and tracked by the radar station shown. when θ reaches 66°, other corresponding measurements give the values r = 32700 ft, r¨ = 85 ft/sec2, and θ˙ = 0.019 rad/sec. calculate the magnitudes of the velocity and acceleration of the rocket at this position.