Which expression correctly gives the impulse delivered by a time-dependent force $F\left(t\right)$ between times $t_1$ and $t_2$?

Which pair of units is valid for impulse in SI?

A force acts during the $1.8$ s interval that begins $0.7$ s after an experiment starts. What are the correct integration limits?

A braking thruster on a probe produces $F\left(t\right)=(9t^2-6t)$ N for $1\text{ s}\le t\le 4\text{ s}$. What is the impulse over this interval?

A force-time graph has two parts: from $0$ to $2$ s, force increases linearly from $0$ N to $6$ N; from $2$ to $4$ s, the force follows $F\left(t\right)=6+(t-2{)}^2$ N. What total impulse is delivered from $0$ to $4$ s?