Define the following propositions: 
 s: a person is a senior 
 y: a person is at least 17 years of age 
 p: a person is allowed to park in the school parking lot 
 Express each of the following English sentences with a logical expression: 
 a. A person is allowed to park in the school parking lot only if they are a senior and at least seventeen years of age. 
 b. A person can park in the school parking lot if they are a senior or at least seventeen years of age. 
 c. Being 17 years of age is a necessary condition for being able to park in the school parking lot. 
 d. A person can park in the school parking lot if and only if the person is a senior and at least 17 years of age. 
 e. Being able to park in the school parking lot implies that the person is either a senior or at least 17 years old