A close friend moved to a planet in the Sirius system, about 8 lightyears away from Earth. When you call him on the phone, assuming he answers immediately, how long would it take you to hear him say "hello" from the time you placed the call? Explain your answers

The answer would be plant growth.

It is the doctrine that the us had the right and duty to expand throughout north america. it just means they believed they had the right to expand westward and they did! they stated with the 13 colonies and then they kept moving gaining different territories throughout the years

H=   2(area/a+b)h= 2(144/a+b)h= 2(144/18+18)h= 2(144/36)h= 2(4)h=8