For each of the following measurements, state (with reasons) whether a DMM or oscilloscope is the more suitable test instrument. a. The DC voltage of a +12 V dc supply rail in a printed circuit board (PCB). b. The RMS voltage across a resistive heater driven by a 48 V ac 60 Hz square wave. c. The RMS current flowing in a resistor connected across the output of a function generator (5 V pp, 800 kHz). d. The RMS voltage across a loudspeaker with a 12 kHz sinusoidal input.