Three employees in the maintenance department are responsible for repairing the video games at Pinball Wizard, a video arcade. A maintenance worker can fix one video game machine every $[$fix$]$ hours on average, with an exponential distribution. An average of one video game machine fails every $[$fail$]$ hours, according to a Poisson distribution. Each down machine costs the Wizard $$30$ per hour in lost income. Each maintenance worker would cost $$16$ per hour. What would be the total operating costs per hour $($including both lost income and labor costs$)$ if a fourth maintenance worker is hired at the same cost?