Urgent

yesterday morning, i got a text message from my friend, steph, asking me how to convert 80 and 8 mg to mL. I said "what's this for? mg is totally different from mL." Steph's neighbor asked her to give her shots of ampicillin and gentamycin (antibiotics). She's asking for the formula for the right dosage of medication. With only a doctor's prescription and 2 vials of ampi and genta in her hand, she has to compute for the right dosage for her neighbor/patient. I was jolted by the moment realizing that I MUST and SHOULD know the formula by heart because it is the most common dosage calculation. I then reach for my pharmacology book and browse the index for ampicillin and gentamycin just to be absolutely sure of the right formula. Steph's messages kept on coming as she reiterates to me if her calculation was accurate. We both arrived at the same answers: 0.4 mL of ampicillin and 1.2 mL of gentamycin are to be administered to the neighbor. Whew! I thought nursing doesn't have Math. I'm poor at Math.