The period of apprenticeship training, which shall be specified in the contract of apprenticeship, shall be as follows:—
(a) in the case trade apprentices who, having undergone institutional training in a school or other institution recognised by the National Council, have passed the trade tests or examinations conducted by That Council or by an institution recognised by that Council the period of apprenticeship training shall be such as may be prescribed;
(b) in the case of other trade apprentices the period of apprenticeship training shall be such as may be prescribed;
(c) in the case of graduate or technician apprentice technician (vocational) apprentice, the period of apprenticeship training shall be such as may be prescribed.