ΜN/(kg⋅ns) in the correct SI of:

μN/ (kg ns) = 10³ N / (kg s)

Explanation:

In this exercise they ask us if the notation is correct. Let's write the different terms in the SI systems

force is N

time is in seconds

the unit given for the force is 1 N = 10⁶ μN

the unit of time is 1 s = 10⁹ ns

the correct way to give the answer should be: N / (kg s)

so the notation should be changed

        μN /kg ns = μN / (kg ns) (1N / 10⁶ μN) (10⁹ ns / 1 s) =

        μN/ (kg ns) = 10³ N / (kg s)

conservation of mass

mass before something happens = mass afterwards