public function filterEsiApplicableApplicants(Collection $applicants): Collection 	{ 		$helper = fn (?int $value): int => $value ? 1 : 0; // determine if question has been answered  		return $applicants->filter(function (Applicant $applicant) use ($helper) { 			return ($helper($applicant->esi_workplace_satisfaction) + $helper($applicant->esi_workplace_expectations) + $helper($applicant->esi_ideal_job_comparison)) >= self::MINIMAL_APPLICABLE_NUMBER; 		}); 	}