The three in series are equivalent to 3*470 = 1410 ohms.
I = E/R = 48 / 1410 = 0.034 amps or 34 mA
Voltage is divided evenly between the three, so 16 volts across each one
total power = 0.034 x 48 = 1.63 watts, divided by 3 that is 545 mW each. so 1 watt resistors will be fine.