For the circuit in Figure P4.47, determine the value of resistors $R_1$ and $R_2$, knowing that the time constant before the switch opens is 1.5 ms , and it is 10 ms after the switch opens. Assume: $R_S=15 \mathrm{k} \Omega, R_3=30 \mathrm{k} \Omega$, and $C=1 \mu \mathrm{~F}$.
(FIGURE CAN'T COPY)
Figure P4.47