8. Find the capacitance of a coaxial cable (shown in Fig. 5) with the following parameters: \( a = 0.500 \, \text{cm} \), \( b = 1.75 \, \text{cm} \), \( L = 30.0 \, \text{cm} \), and \( \kappa = 2.3 \) (dielectric constant of polyethylene). (\( k{\nu} = 8.9876 \times 10^{9} \, \text{Nm}^2/\text{C}^2 \) or \( \varepsilon0 = 8.8542 \times 10^{-12} \, \text{C}^2/\text{Nm}^2 \)) (以科學記號表示且四捨五入至小數點3位) (10 points)