The volume of a rectangular prism can be calculated using this formula:

Where "l" is the length, "w" is the width and "h" is the height.
In this case, you know that the dimensions of the section are:

Therefore, substituting values into the formula and evaluating, you get that its volume is:
![V_{\text{section}}=(15\operatorname{cm})(12m)(3m)=540m^3]()
According to the explanation given in the exercise, each person requires this volume of air space:

Then, to find the number of people it can hold, you need to set up that:

Hence, you get:

Therefore, the answer is: 90 people.