A raft of wood(density=600 kg/m^3) of mass 120 kg floats in water.how much weight can be put on the raft to make it just sink

we know that

weight of water displaced = weight of raft + mass

so,

ρ_wVg = Mg

here, M = mass of raft + mass = (120+m) kg

thus,

ρ_w=1000 kg m-3

ρ_wVg = (120+m).g

m + 120 = ρ_wV = 1000 x V

so,

m + 120 = 1000 x V

V(volume of water displaced=Volume of raft)=120/600=.2 m³ 

m=.2x1000-120

m=80 kg