def derivativeY(self,mLvl,pLvl,MedShk):
        '''
        Evaluate the derivative of consumption and medical care with respect to
        permanent income at given levels of market resources, permanent income,
        and medical need shocks.

        Parameters
        ----------
        mLvl : np.array
            Market resource levels.
        pLvl : np.array
            Permanent income levels; should be same size as mLvl.
        MedShk : np.array
            Medical need shocks; should be same size as mLvl.

        Returns
        -------
        dcdp : np.array
            Derivative of consumption with respect to permanent income for each
            point in (xLvl,MedShk).
        dMeddp : np.array
            Derivative of medical care with respect to permanent income for each
            point in (xLvl,MedShk).
        '''
        xLvl = self.xFunc(mLvl,pLvl,MedShk)
        dxdp = self.xFunc.derivativeY(mLvl,pLvl,MedShk)
        dcdx = self.cFunc.derivativeX(xLvl,MedShk)
        dcdp = dxdp*dcdx
        dMeddp = (dxdp - dcdp)/self.MedPrice
        return dcdp,dMeddp