12 shall be paid in monthly installments: the principal is 5000÷ 12+ the handling fee is 5000x0.67% = 416.67+33.5 = 450.17 yuan.
18 shall be paid in monthly installments: principal 5000÷ 18+ handling fee 5000x0.67% = 277.78+33.5 = 311.28 yuan.
24 installments should be repaid every month: principal 5000÷24+ handling fee 5000 x 0.70% = 208.33+35 = 243.33 yuan.