Suppose two drugs are routinely used for the treatment of thyroid dysfunction. drug x is known to cure the disorder 75% of the time and costs $88. drug y is known to cure the disorder 60% of the time and costs $75. the two drugs work independent of each other. the two treatment plans are as follows: plan a: treatment with drug x—if not effective, treatment with drug y plan b: treatment with drug y—if not effective, treatment with drug x for what part of the population is plan b not effective? 40% 30% 15% 10%