Break-Even in Sales Revenue

Big Red Motors, Inc., employs 15 sales personnel to market its line of luxury automobiles. The average car sells for $75,000, and a 6 percent commission is paid to the salesperson. Big Red Motors is considering a change to the commission arrangement where the company would pay each salesperson a salary of $1,600 per month plus a commission of 2 percent of the sales made by that salesperson. What is the amount of total monthly car sales at which Big Red Motors would be indifferent as to which plan to select?(CMA adapted)

please include where each value is retrieved from and why each step is taken in the equation