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section 2.7 checkpoint: #2.19, 2.20, 2.21; ~~section 2.8 checkpoint: #2.23, 2.26, 2.27~~, and the following problem:

*Problem A*: Consider the ideal gas law from chemistry: $pV=NRT$, where $p$ represents pressure, $V$ represents volume, $N$ represents the amount of a substance, $R$ is the gas constant, and $T$ is the temperature. This equation can be algebraically rearranged to obtain $R=\dfrac{pV}{NT}$. Write a program to ask a user to input values for the variables $p$, $V$, $N$, and $T$ and then calculate and print the value of $R$ in response.