Given the task definition and input, reply with output. In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Question: Mrs. P. R. has prescribed a serum therapy at a rate of 2 liters of isotonic saline in 24 hours; How many drops / minute would the infusion graduate ?:
Options: <1> twenty. <2> 24 <3> 28 <4> 32 <5> 36
3