Marta's adventure in the ocean!

Martha is going scuba diving. She has a medium sized air tank that can hold $30$ minutes of air. Her friend Samantha, however, has a large air tank that can hold $45$ minutes of air. Before diving in the ocean, Martha and Samantha read a sign that says:

Remember:

These following noises will take the standard amount of air in the following ratios:

Screaming: 5 minutes of air per minute of screaming

Crying: 3.5 minutes of air per minute of crying

Normal: 1 minute of air per minute of being normal

If Martha and Samantha want to empty their tanks at the same time, what is the maximum number of minutes that Samantha could cry? Assume that Samantha can only cry in an integer amount of time.