4. For the purposes of these regulations an eligible agricultural business is an agricultural business which appears to the appropriate Minister to be suitable for development and as to which that Minister is satisfied—
(a)that the earned income per labour unit reasonably required under the existing system of production is less than the comparable income determined in accordance with regulation 13(a), or
(b)that the nature or structure of the business is such as to place at risk the maintenance of an earned income at the level of the comparable income determined as aforesaid.