The answer is 33%, how did they get this?

In the phase diagram for the Cu-Ni system shown below, consider the point B in the L+ region. If the L and boundary lines are intersected at the values shown on the x-axis (CL=28%Ni and CR=39%Ni), and you are given that the weight fractions of the L and phases at B is 0.545 and 0.455 respectively, calculate the approximate concentration C0(wt%Ni) at point B