A circular conducting loop is held fixed in a uniform magnetic field that varies in time according to B(t)=B₀​exp(−at), where t is in seconds, a is in s⁻¹, and B is the field strength in Tesla at t=0. At t=0, the emf induced in the loop is 0.0609V. At t=1.97s, the emf is 0.0448V. Find a.