Zara operates a delivery company that specializes in transporting goods across the city. Her fleet consists of $600$ vehicles, divided evenly between vans and trucks. Each vehicle undergoes routine maintenance and checks at Leo's workshop. On average, a van is sent to the workshop $5$ times every month, and a truck is sent to the workshop $3$ times every month $($assuming $30$ days in a month$).$ When sent for maintenance, each vehicle remains in the workshop for an average of $1\mathrm{.}7$ days before being declared fit for service again.What is the average number of Zara's vehicles out of service in Leo's workshop?