how to generate random population of GA with decimal constraint

 i have to max this function max f(x1,x2)=21.5+x1sin(4pix1)+x2sin(20pix2) where -3<=x1<=12.1 4.1<=x2<=5.8 using genetic algo i have to maximize and for ga i have to encode these x1 x2 into binary strings. i want to genrate an initial population of x1 and x2 in binary form with in this decimal range
%Binary number generation
P = randi([0,1],5,33)  % Generate a 5-by-33 random binary matrix.
c=P(1:5,1:18);  % x1 values extraction rom random population
d=P(1:5,19:33);
x1=bi2de(c);    %conversion of x1 values to decimal
x2=bi2de(d);
f=zeros(1,5);
for i=1:5
f(i)=21.5+x1(i,1)*sin(4*360*x1(i,1))+x2(i,1)*sin(20*360*x2(i,1));
f(1,i)=f(i);
end
f      %evaluation of fitness values
F=sum(f) %total fitness of the population
right now i have coded this but my problem is the population of binary number which is being generated randomly is not with in constraint of x1 and x2.