How can I solve this?
I managed to find Part A, but I got stuck trying to find Part B and C

Parte B : 31.18º , Parte C: 31.17º

Explanation:

Parte B: The angle between the glass and the water before it enters the water is going to be equal to the value of the angle when it enters the glass , 27.13º.

Using the formula n1 senθ1 = n2 senθ2 , where n1=1.51 , θ1=27.13º, n2=1.33 , it gives us θ2=31.18º.

Parte C: n1= 1 , θ1=43.5º, n2=1.33

Using the same formula : n1 senθ1 = n2 senθ2 , it gives us θ2= 31.17º.

double the distance = divide strength by 4

a.   mass number from atomic number