In this diagram, how many foreign keys does the Shipment table contain?

$\backslash$table$[[$Customer$,$Shipment$],[$cust$\_$id$,$ship$\_$id$],[$cust$\_$name,cust$\_$id$],[$annual$\_$revenue,weight$],[$cust$\_$type,truck$\_$id$],[$address$,$driver$\_$id$],[$city$,$city$\_$id$],[$state$,$ship$\_$date$],[$zip$,$city$\_$id$],[$phone$,$city$\_$name$],[,]]$

Truck

truck$\_$id

make

model year

$\backslash$table$[[$Driver$],[$driver$\_$Id$],[$first$\_$name$],[$last$\_$name$],[$address$],[$city$],[$state$],[$zip$\_$code$],[$phone$]]$

$4$

$2$

$1$

$3$