no you will not get 40 lbs from 30 seeds,you are dreaming if this is your first grow.
you would be better to get a female plant good genes, big yielder & grow her so you can clone 100 + babys from her,or get 5 mother plants and start at early spring and clone 50 + babys ever 3 weeks until early to mid summer and prepare to be busy.
but really if you want to grow shitloads of shit outside you have to start in the off season prepareing your holes digging them adding all the goodies and letting them sit until you are ready in the spring.
there are techniques out there so you dont have to grow a 15 foot plant to get a good yield from it
& good luck