Under her cell phone plan, Nevaeh pays a flat cost of $46.50 per month and $5 per gigabyte, or part of a gigabyte. (For example, if she used 2.3 gigabytes, she would have to pay for 3 whole gigabytes.) She wants to keep her bill under $55 per month. What is the maximum whole number of gigabytes of data she can use while staying within her budget?