Question: Fast Courier is a US transport company located in Wichita, Kansas, that specializes in

door$-$to$-$door deliveries. The company owns a fleet of $14$ vans and turns to third parties for hiring

vans in case the service demand exceeds the fleet capacity. Last year, the number of vans weekly

used for meeting all the transport demand is reported in Table $1.$

Table $1$: Weekly number of vans used by Fast Courier last year

For next year, the company has decided to redesign the fleet composition, with the aim of reducing

the annual transport cost, assuming that the vehicle requests remain identical to those of the year

just ended. Assuming that $cF=$$$350,cV=$$$150$ and $cH=$$$800,$ find the optimum number of vans.