Executive Administration must be invited since it has the greatest number of employees. Technical Support, even though they have the second most employees, their attendance is influences the Executive Administration department attendance and since the latter has more employee Technical support should not be invited if you want to ensure the greatest possible number of employees to accept the invitation since you can only invite 2 departments. All other departments are a guaranteed 12 employees. Thus it will be 18 + 12, as opposed to 15 + 12.