400 watt hps or CFL'S

in the (buds for less. SEEMOREBUDS book) they start flowering at day 16 using "CFL'S",.............with the 400w hps when would i have to start flowering?
 
sorry for butting in! but how much does a 400w bulb & ballaste cost$ ???
and can i use the same bulb for veg & flower phases?
 
how do i measure the ammount of nutes that is suposed to go into my plant?
wasnt it parts per million or something like that???
 
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