A cannon fires successively two shells with velocity v₀ = 250 m/s; the first at the angle ${\mathrm{\theta }}_1$ =53^o and the second at the angle ${\mathrm{\theta }}_2$ =37° to the horizontal, in the same vertical plane. Neglecting the air drag, find the time interval in seconds between firing leading to the collision of the shells.(Take, g = 10 m/s²)