Determine whether each of the following sets of events is mutually exclusive.
a. Five coins are tossed: “no more than one head is observed,” “two heads are observed,” “three or more heads are observed.”
b. A salesperson calls on a client and makes a sale: the amount of the sale is “less than $100,” is “between $100 and $1000,” is “more than $500.”
c. One student is selected at random from the student body: the person selected is “female,” is “male,” is “older than 21.”
d. Two dice are rolled: the numbers of dots showing on the dice are “both odd,” “both even,” “total 7,” “total 11.”