PF5 involves sp3d hybridisation and hence has trigonal bipyramidal structure.
In PCl5 the central atom is surrounded by five bond pairs and no lone paris.
Hybridisation of central atom in PCl5 molecule is sp3d giving trigonal bipyramidal shape.
In [Fe(CO)5], oxidation state of CO is zero.
It has hybridisation =dsp3.
So it has trigonal bipyramidal geometry.
BrF5; square pyramidal
[PtCl4]−2; square planar
BF3; Trigonal planar.
Hence the answer is 3