Hey everybody i hope your doing ok

You are getting ready to transport troops in a m1152 configured with cargo cover and troop seats which of the following should you do before starting out

Earth's atmosphere is unique among the planets and is able to support life because it contains a large amount of a) oxygen b) helium c) methane d) carbon dioxide

How many liters of 60% alcohol solution should be added to 40 liters of a 20% alcohol solution to make a 50% solution?