We will use The Law of Cosines for finding the angle <C:

c^2 = a^2 + b^2 - 2ab cos(<C)

<C means the same as m C

cos(<C) = (a^2 + b^2 - c^2)/(2ab)

a = 4, b = 5, c = 4.12

cos(<C) = (4^2 + 5^2 - 4.12^2)/(2*4*5)

cos(<C) = 0.60064

<C = arccos(0.60064)

<C = 53 degrees approximately that is

m C = 53 degrees