AS the compound is having cn =4 so it ican have two possible hybridisation sp³ or dsp². as the spin only magnetic momet is 5.9 so it implies thst it is having 5 unpaired d electrons which is poosible in sp³ .there for it will have tetrahedral shape and sp³ hypridisation. moreover  Br is a weak ligand so it will occupy outer orbital complex and will show sp³ hybridisation.