Mack Back owns a pool supply store in a convenience shopping center.

At the beginning of this year, the following sales associates were on Mack's payroll: Mark Park, Cheryl Merrill, Joyce Royce, and Mack's two sons, Jack and Zach.

A few months into the year, Joyce and Cheryl both left to pursue new opportunities, and Mack hired Gray Bray and Matt Pratt to replace them.

A few months after that, Jack and Zach left to go to college full time. They were replaced by Braxton Paxton and Miller Stiller.

What is the employee turnover rate at Mack's store, if no more employees leave between now and December $31?$

$30$ percent

$40$ percent

$50$ percent

$60$ percent

$80$ percent