Four, a certain project, if contracted by Team A and Team B, can be completed in $2 \frac{2}{5}$ days, with a payment of 1800 yuan; if contracted by Team B and Team C, it can be completed in $3 \frac{3}{4}$ days, with a payment of 1500 yuan; if contracted by Team C and Team A, it can be completed in $2 \frac{6}{7}$ days, with a payment of 1600 yuan. Under the condition of ensuring the project is completed within one week, which team should be chosen to contract the project alone to minimize the cost?