Which point on Figure E5-1 best represents the impedance of a series circuit consisting of a 400-ohm resistor and a 38-picofarad capacitor at 14 MHz?

To find the correct point, you must first calculate the capacitive reactance using the formula Xc = 1 / (2 * pi * f * C). Plugging in 14 MHz (14,000,000 Hz) and 38 pF (0.000000000038 F) yields approximately 300 ohms. Because the component is a capacitor, the reactance is negative (-j300). The resistance is given as 400 ohms. In the rectangular coordinate system, you move to +400 on the horizontal X-axis (resistance) and down to -300 on the vertical Y-axis (capacitive reactance), which corresponds to Point 4 on the exam's standard figure.