(1) "Employment" does not include casual labor not in the course of the employer's trade or business performed in any calendar quarter by an employee, unless the cash remuneration paid for the service is fifty dollars or more and unless the service is performed by an individual who is regularly employed by the employer to perform such service. For purposes of this section, an individual is deemed to be regularly employed during a calendar quarter only if:
(a) On at least twenty-four days during such calendar quarter, the individual performs services for the employer which are not in the course of the employer's trade or business; or
(b) On at least twenty-four days during the previous calendar quarter, the individual performed services for the employer which were not in the course of the employer's trade or business.