Answer:
I believe the answer is B.
Answer:
E=3 x 10^4 N/c
Explanation:
The electric field strength can be found out disk with a uniform positive surface charge density by

σ= charge density
r= radius of the disk
z= position in which we have to find electric field = 15 cm
ε_0= constant ( vacuum permitivity)
putting values we get

solving we get
E=30000 N/c
E=3 x 10^4 N/c
Density =Mass/volume
When mass is constant, density is inversely proportional to volume or vice versa
When volume decreases, density increases
Hope it helps