Name the customer who sent the shipment to Oak Park.
"Oak Park" is the city_name; customer name refers to cust_name
SELECT T2.cust_name FROM shipment AS T1 INNER JOIN customer AS T2 ON T1.cust_id = T2.cust_id INNER JOIN city AS T3 ON T3.city_id = T1.city_id WHERE T3.city_name = 'Oak Park'