A first order reaction has a specific reaction rate of $10^{-2}sec^{-1}$. How much time will it take for 20 g of the reactant to reduce to 5 g?
(a) 138.6 sec
(b) 346.5 sec
(c) 693.0 sec
(d) 238.6 sec
(a) 138.6 sec
(b) 346.5 sec
(c) 693.0 sec
(d) 238.6 sec