To find the deflection at point C of the beam, first determine the reactions at points A and B to achieve equilibrium. The modulus of elasticity (E) and moment of inertia (I) are essential for calculating the deflection, with various formulas applicable depending on the beam's conditions. The deflection at C can be approximated by summing the deflections from specific cases, acknowledging that the beam's support at B is not fixed. For precise calculations, analyzing the beam from first principles is recommended. Understanding these factors will lead to an accurate measurement of deflection in millimeters.