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Answer:
15.8 V
Explanation:
The relationship between capacitance and potential difference across a capacitor is:

where
q is the charge stored on the capacitor
C is the capacitance
V is the potential difference
Here we call C and V the initial capacitance and potential difference across the capacitor, so that the initial charge stored is q.
Later, a dielectric material is inserted between the two plates, so the capacitance changes according to

where k is the dielectric constant of the material. As a result, the potential difference will change (V'). Since the charge stored by the capacitor remains constant,

So we can combine the two equations:

and since we have
V = 71.0 V
k = 4.50
We find the new potential difference:

Classius claperyon equation
In (P2/ P2) = ΔHvap/R) × (1/T2-1/T1)
T2 occurs at normal boiling when vapor pressure P2 = 1 atm.
P1 = 55.1 mmHg, P2 = 1 atm = 760mmHg
T1 = 35°c = 308.15k, T2 =
ΔHvap = 32.1kJ/mol = 32100 J/mol
In (760/55.1) = (-32100/ 8.314) × ( 1/T2 - 1/308.15)
The normal boiling point T2 = 390k = 117°c