a)

Now, this is absolute pressure, so we need to subtract atmospheric pressure (101 kPa or so), so the gauge pressure is

b) Does the obstruction completely block the syringe? If so then there is exactly 1 N of force. The fluid (presumably) will not compress and thus transmits forces perfectly.

c)

So we need to exert at least this much pressure. Thus

Thus

(Edit: That's amuchnicer answer! )

-Dan