Given the two tables described below, which of the following queries will display number of orders shipped?

customer: with the fields customerid(PK), lastname, firstname

order: with the fields orderid(PK), orderdate, shipdate, customerid(FK)

1. SELECT COUNT(shipdate) FROM order;

2. SELECT COUNT(*) FROM order WHERE shipdate IS NULL;

3. SELECT COUNT(*) FROM order WHERE orderdate IS NOT NULL;

4. SELECT COUNT(shipdate) FROM order GROUP BY customerid;