How to find bits you need to represent one variable? How many integers( 16 or 32 bits) you need when

you use binary coded GA(Genetic algorithms), your problem is to find vector with real numbers, which are between [0,5] and you want your answer at least to three decimal places(0.001). a) How many bits you need to represent one variable b) the dimension of your problem is 10 or you optimize ten variables. How many integers( 16 or 32 bits) you need when programming the problem, in case you use bit-fields, in which you have reserved for each variable the bits it exactly needs?