A telephone call center uses five customer service representatives $($CSRs$)$ during the $8$:$30$ a$.$m$.$ to $9$:$00$ a$.$m$.$ time period. The standard service rate is $6\mathrm{.}0$ minutes per telephone call per CSR$.$ Assuming a target labor utilization rate of $80$ percent, how many calls can these five CSRs handle during this half$-$hour period? Round your answer to the nearest whole number.

calls