A circular conducting loop is held fixed in a uniform magnetic field that varies in time according to B(t) = B0exp(−a t) where t is in s, a is in s−1 and B is the field strength in T at t = 0. At t = 0, the emf induced in the loop is 0.0661 V. At t = 1.54 s, the emf is 0.0192 V, .Find a. Answer in units of s−1.