The Switch in the Circuit Shown Below Has Been Closed $= 0$

Essay

the switch in the circuit shown below has been closed for a long time before it is opened at t $= 0$ . Find the voltage $\mathrm { v } ( \mathrm { t } )$ across the capacitor for $\mathrm { t } \geq 0$ . Assume $\mathrm { R } _ { 1 } = 1.8 \mathrm { k } \Omega , \mathrm { R } _ { 2 } = 12 \mathrm { k } \Omega , \mathrm { R } _ { 3 } =$ $2.8 \mathrm { k } \Omega , \mathrm { R } _ { 4 } = 18 \mathrm { k } \Omega , \mathrm { V } _ { \mathrm { s } } = 3 \mathrm {~V} , \mathrm { C } = 0.02 \mu \mathrm { F }$ .