Add spaces: Thisisalsocalledtheprincipalquantumnumberfortheelectron.

Answer: This is also called the principal quantum number for the electron.

Add spaces: Choosecategoryorallergenfilter(0)

Answer: Choose category or allergen filter (0)

Add spaces: Howevertheywereonlysendingabout$1billionthroughofficialchannels.

Answer:
However they were only sending about $1 billion through official channels.