First it’s important to check units, we notice that the dimensions are given in mm. Therefore in order to convert this to m^3 we need to multiply the volume in mm by (10^-3)^3 which gives us 2.64 x 10^-9.Next density is given by d=M/V. Therefore the answer is 0.5/2.65 x 10^-9 = 1.89 x 10^8