def calc_labour(yield_potential):
    """
            Labour Costs Formaula
            Notes
            ------
                Direct farm labour cost = Number of staff working full-time x wages x 30 hours
                Generalisation if statement on farm labour required if unknown
    """

    farm_hours = yield_potential*0.2
    labour_cost = farm_hours * 7 # wage
    return labour_cost