double MaxLoiNhuan(double a) { double t = 0; if (a <= 1000) { t = 1.15; } else if (a <= 5000) { t = 1.1; } else if (a < 100000) { t = 1.07; } else if (a < 1000000) { t = 1.05; } else { t = 1.02; } return(t); }