The decision to use or not to use a particular drug 1' is represented by a 0-1 variable 61: for each drug. Formulate the following conditions by means of integer programming constraints. In If drug A is used in treatment then drug B must also be used. I If drug C is used then we cannot use drug D nor can we use drug 8. o If drug D is used then either drug A or drug E (or both) must also be used