First, sum up the total expenses for the original plan
Duque de Caxias + Campinas + Rio de Janeiro + Guarulhos = 242+185+193+120 = R$740
It is clearly over the intended budget. The average cost per itinerary is around R$200 so we will consider making a swap on either Duque de Caxias and Rio de Janeiro. Possible answers are (b) or (c)
for (b) Replace Duque de Caxias with Fortaleza, we will have
Fortaleza + Campinas + Rio de Janeiro + Guarulhos = ⇒ 201+185+193+120 = R$699 ⇒ This is exactly the budget intended for the trip for (C) Replace Rio de Janeiro with Porto Alegre Duque de Caxias + Campinas + Porto Alegre + Guarulhos = ⇒ 242 + 185 + 153 +120 = R$ 700 ⇒ This is over R$1
