Consider the following premises. Sarah is drinking water if and only if Mary is driving a car. If Sarah drinks water, then Mary is driving a car. Mary is driving a car. Can we infer the following from them? Sarah is not drinking water.
 From the fact that Sarah is drinking water if and only if Mary is driving a car we can infer that if Mary drives a car, then Sarah is drinking water. From the fact that if Mary drives a car, then Sarah is drinking water, and that if Sarah drinks water, then Mary is driving a car we can infer that Mary is driving a car if and only if Sarah is drinking water. From the fact that Mary is driving a car if and only if Sarah is drinking water we can infer that if Mary drives a car, then Sarah is drinking water. Finally, from the fact that if Mary drives a car, then Sarah is drinking water, and that Mary is driving a car we can infer that Sarah is drinking water, which contradicts that Sarah is not drinking water. Therefore, the answer is no.