A permanent magnet for an MRI scanner is made by removing extraneous elements from an ore containing rare earth elements to leave elements Pr and Nd therein, and then selectively stripping therefrom a portion of the element Nd as a byproduct to leave an ore residuum including both elements Pr and Nd therein. A first method comprises introducing into a host microorganism a plurality of heterologous nucleic acid sequences, each coding for a different enzyme in the mevalonate pathway for producing isopentenyl pyrophosphate. The method comprises: a first analyzing step for analyzing whether the second device is using the first data provided by the first device; a step for controlling, based on the result of the first analyzing step, the working status of the first device.