Household electricity is supplied in the form of alternating current that varies from 155 V to -155 V with a frequency of 60 cycles per second (Hz). The voltage is thus given by the equation $$E(t) = 155 \sin(120 \pi t),$$ where $t$ is the time in seconds. Voltmeters read the RMS (root-mean-square) voltage, which is the square root of the average value of $[E(t)]^2$ over one cycle.

(a) Calculate the RMS voltage of household current.

RMS voltage =

(b) Many electric stoves require an RMS voltage of 220 V. Find the corresponding amplitude $A$ needed for the voltage $E(t)=A \sin(120\pi t).$

{\it A} =