Three melt-spun fibre samples A, B and C produced from same polymer under different conditions are found to have densities 1.10 g/cm3, 1.15 g/cm3 and 1.20 g/cm3, respectively. If the mass fraction based degree of crystallinity (xc) of A and C is 0.45 and 0.75, respectively, then xc for B (rounded off to 2 decimal places) is___