78.4. An individual who is employed in the year as a musician and, as a term of the employment, is required to provide a musical instrument for a period in the year may deduct an amount not exceeding his income for the year from the employment, computed without reference to this section, equal to the aggregate of(a) amounts disbursed by him before the end of the year for the maintenance, rental and insurance of the instrument for that period, except where the amounts are otherwise deducted in computing his income for any taxation year, and
(b) such part of the capital cost of the musical instrument as is allowed by regulation.