HELP NO LINKS JUST A SERIOUS ANSWER WIT WORK

Given that the density of air is 1.225 kg/m3 at Standard Temperature and Pressure (STP, Sea Level) and: 2.205 lb = 1 kg, 39.37 in = 1 meter, 32.2 lb = 1 slug, 12 in = 1 ft,

1) What is the density of air (at STP) in slug/ft3 ?

2) What is the density of air (at STP) in lb/ft3 ?

3) What is the density of air (at STP) in lb/in3 ?

4) Assuming that the density of air varies linearly with altitude from Sea Level where it is 1.225 kg/m3 to 55,500 ft altitude where it is assumed to be 0.0, determine what the air pressure in lbs/in2 is at Sea Level.

5) Using the same assumptions as in #4 what would the air pressure be at 40,500 ft of altitude?