Elevation in boiling point for 1.5 molal solution of glucose in water is 4 K. The depression in freezing point for 4.5 molal solution of glucose in water is 4 K. The ratio of molal elevation constant to molal depression constant $\left({\mathrm{K}}_{\mathrm{b}}/{\mathrm{K}}_{\mathrm{f}}\right)$ is