Answer:
C. -12 ab
Explanation:
The restoring force on a spring is given by Hooke's law:

where
k is the spring constant
x is the stretched (or compressed) displacement of the spring
In this problem we have:
k = 4a
x = 3b
Substituting into the equation, we find:

And the negative sign means that the direction of the force (negative) is opposite to the direction of the displacement (positive).
Drinking Water - Direct
Our Eating Habits - Direct
Washing Clothes - Indirect
My science teacher said that there is no equivalent unit to a newton
Convert 10mm to metres = 0.01m
Wave speed = frequency *wavelength
= 4Hz*0.01m
= 0.04 m/s
Hope this helps