Two identical calorimeters of negligible heat capacities are filled with two liquids $\mathrm{A}$ and $\mathrm{B}$ whose densities are in the ratio $4:3$. The ratio of times taken in cooling from $80{ }^{\mathrm{o}}\mathrm{C}$ to ${\text{75 }}^{\mathrm{o}}\mathrm{C}$ is $5:6$. The ratio of their specific heats is

Two large holes are cut in a metal sheet, as shown below. If this is heated, distance $AB$ and$BC$

Two rods having length $l_1$ and $l_2$, and made of materials with the linear expansion coefficient ${\alpha }_1$ and ${\alpha }_2$, respectively, were soldered together. The equivalent coefficients of linear expansion for the obtained rod is: