VI$$s call center operates from $10$ a$.$m$.$ to $10$ p$.$m$.$ daily with $4$ sales representatives and receives calls at a rate of $50$ per hour following a Poisson distribution. It takes an average of $4$ minutes to handle each call with actual times being exponentially distributed. The phone system VI uses can keep up to $10$ callers on hold at any time. Assume those who receive a busy signal don$$t call back.