To solve this problem it is necessary to apply the concepts related to the concept of superposition and the fringe separation for double slit experiment.
The equation can be written as

Where
= Distance between fringes
x = distance between slits and screen
d = Distance between slits
= Wavelength
Our values are given as
d= 0.08mm
x =3m

In this way replacing in the equation,




Therefore the distance between the fringes is 2.37cm
PART B) For the case in which it is submerged in water it is necessary to apply the relationship of the fringes with the index of refraction therefore



Answer:
Both of them are correct
Explanation:
Here both the technician are correct. A special puller and installer tool is required to remove and install the vibration damper. Removing and installing a damper is not an easy task, it requires a definite set of technique and tools.
According to Technician B if the inertia ring on the vibration damper is loose, the damper must be replaced is absolutely correct, inertia ring once loosened cannot be tightened. hence, we have change the the damper.