farm utensils, (3) tools of a mechanic’s trade, and (4) boats, fishing gear and nets up to a value of $10,000 owned and actually used in the individual’s business if engaged exclusively in commercial fishing. [G.L. c. 59, § 5, cl. 20]. B. BUSINESS CORPORATIONS as defined in G.L. c. 63, § 30 and taxable under G.L. c.