Answer:
To calculate the cross-sectional area of the pipe, we can use the following equation:
```
A = m / (C * D * t)
```
where:
* A is the cross-sectional area of the pipe (m^2)
* m is the mass of methane that diffuses out of the tank (kg)
* C is the concentration of methane in the tank (kg/m^3)
* D is the diffusion constant for methane in air (m^2/s)
* t is the time that the valve is left open (s)
We are given the following values:
* m = 6.10×10^-4 kg
* C = 0.740 kg/m^3
* D = 2.10x10^-5 m^2/s
* t = 10.0 * 3600 s
Substituting these values into the equation, we get:
```
A = 6.10×10^-4 kg / (0.740 kg/m^3 * 2.10x10^-5 m^2/s * 10.0 * 3600 s)
```
```
A = 0.0010903760903760902 m^2
```
Therefore, the cross-sectional area of the pipe is **0.0010903760903760902 m^2**.
Step-by-step explanation:
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