I do not understand what is actually supposed to be calculated in the question below?

Last Group has a rental cost of €25,000 per month with a four-year lease term. Casual staff are employed on a weekly basis to carry out telephone sales. The cost of casual staff is €12,000 per month and telephone call costs are €5,000 per month. An offshore call centre has offered to carry out the telephone sales activity from its own premises and using its own staff and telephone services for a fixed payment of €15,000 per month. Should Last Group accept or reject the outsourcing proposal from the call centre? Please show all calculations.