Inside a parallel plate capacitor the electric field E varies with time as t2. The variation of induced  magnetic field with time is given by :

For a given plate circumference = L (constant ) and area of plate = A (constant)∫Bdl  =  μ0iD=μ0ε0  dϕEdtBL=μ0ε0  A  dEdtB  ∝   dEdtdBdt  ∝   d2Edt2........(1)E=kt2dEdt  =  2ktd2Edt2=2k=constant⇒   dBdt  =  constant