A patient is intubated. The nurse has to perform a spontaneous breathing trial (SBT) on this patient. For how long should this trial be done?

a. At least 15 minutes but not more than 30 minutes
b. At least 30 minutes but not more than 60 minutes
c. At least 30 minutes but not more than 120 minutes
d. At least 60 minutes but not more than 120 minutes