A fleet of forklift trucks is being planned for a new warehouse. The average travel distance per delivery will be $500$ ft loaded and the average empty travel distance will be $400$ ft$.$ The fleet must make a total of $50$ deliveries$/$hr$.$ Load and unload times are each $0\mathrm{.}75$ min and the speed of the vehicles $=350$ ft$/$min$.$ Assume the traffic factor for the system $=0\mathrm{.}85,$availability $=0\mathrm{.}95,$ and worker efficiency $=90\%.$ Determine number of trucks required to accomplish the $50$ deliveries$/$hr$.$