See,If we take range= 5m (nearer edge of boat), then angle comes out to be 15⁰ or 75⁰

and if we take range= 6m(far end of boat) then angles come out to be 18.5⁰ or 71.5⁰

so, angle(min)= 15⁰ and angle(max)= 75⁰

but in the intervel 18.5 - 71.5⁰ apple will fall outside the boat.