[填空题]
A heart pacemaker is designed to operate at.) fpzk7*p:uaa; kt rm 72 beats/minu-m fc( /jlc:2e0 ikfk using a $7.5-\mu F$ capacitor in a simple RC circuit. What value of resistance should be used if the pacemaker is to fire (capacitor discharge) when the voltage reaches 63% of maximum? $ \times10^{-5 }\;\Omega$
