Monosomics and trisomics are usually inviable in Drosophila, with the exception of those on chromosome 4. The eyeless gene (ey) is recessive to normal eye and is found on chromosome 4. Determine the probabilty of haplo-4 eyeless (ey) F1 progeny when a diplo-4 normal eyed female (ey⁺ ey⁺) is crossed with a haplo-4 eyeless male (ey).