Patients who are addicted to cocaine are sometimes using the drug to combat depression. as such, sometimes addicts are given antidepressant medications to prevent relapse. a three-year study compared the effects of two such medications, lithium and desipramine, along with a placebo for 72 cocaine users wishing to break the habit. the patients were put into 3 groups of 24, and given 1 of the 3 treatments at random. this two-way table illustrates the results. treatment relapse no relapse total desipramine 10 14 24 lithium 18 6 24 placebo 20 4 24 total 48 24 72 give a conditional relative frequency for relapse among patients who took lithium. a. 18/72 = 25% b. 27/72 = 33.33% c. 18/24 = 75% d. 48/72 = 66.67%