a particle is projected from the ground with velocity 50.96 m/s at an angle tan^-1 5/12 to the horizontal .on its upward path it just passes over a wall 14.7 m high. during its flight it also passes over a wall 18.375 high. show that the second wall must not be less than 23.52 m and not more than 70.56 from the first wall

so far ive gotten here : initial speed in the y direction =19.6 first wall is 14.7 m high 14.7=19.6t-4.9t^2 when i solve this t=1 t=3 it must be 1. distance in the x is 47.04 when it just passes over the first wall i then tried to find tried to find the time when its travelled 47.04+23.52 but it wouldnt work dont really know what to do next