An ac voltmeter connected between points $\mathrm{A}$ and $\mathrm{B}$ in the circuit below reads $36 \mathrm{~V}$. If it is connected between $\mathrm{A}$ and $\mathrm{C}$, the reading is $39 \mathrm{~V}$. The reading when it is connected between $\mathrm{B}$ and $\mathrm{D}$ is $25 \mathrm{~V}$. What will the voltmeter read when it is connected between A and D?) Assume that the voltmeter reads true rms voltage values and that the source generated a pure ac.)