eeBee Company has three assembly labor classifications: S$-1,$ S$-2,$ and S$-3.$ The three classifications are paid $$16,$ $$19,$ and $$22$ per hour, respectively. The assembly activity r a product uses an S$-2$ employee, who performs that task in $24$ minutes. To reduce the activity cost per unit, a product engineer proposes using a higher$-$rated employee ho can perform the assembly in $21$ minutes. A manager proposes using a lower$-$rated employee who can perform the assembly in $30$ minutes. Which of the following provides he most cost$-$effective solution?

a$.$ use the $S-3$ employee

b$.$ use the S$-1$ employee

c$.$ use either the $S-1$ or $S-3$ employee

d$.$ use the S$-2$ employee