Ask the DSO. They should be advising you all along on this one.
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Your question is a little bit confusing. Please clarify whether you are asking about working on CPT or OPT. If it is OPT, are you on a STEM extension? You also mentioned in the first part of your question that you are "a fulltime student." Are you currently enrolled and attending classes. If so, then the maximum hours you may be able to work is 20 hours. If you clarify this information I may be able to help you a little more.
There are many restrictions on CPT depending on the number of units taken - on campus job, maximum number of hours and work related to field of study. I would start by talking to my DSO.
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