6. Intro to Forces (Dynamics)

A $5.00$-kg crate is suspended from the end of a short vertical rope of negligible mass. An upward force $F\left(t\right)$ is applied to the end of the rope, and the height of the crate above its initial position is given by $y\left(t\right)=$ ($2.80$ m/s)t + ($0.610$ m/s³)t³. What is the magnitude of $F$ when $t=4.00$ s?