From the curve on the graph we can see, when y=50 x=4.5
the unit of x-axis is in "billions of years", so the answer is 4.5 billions of years
Molecules and polyatomic ions are formed by covalent bonds.
Answer:

Explanation:
Temperature of the house, 
Convert to rankine, 
Heat is extracted at 40°F i.e 
Calculate the coefficient of performance of the heat pump, COP

The minimum power required to run the heat pump is given by the formula:
...............(*)
Where the heat losses from the house, 
Substituting these values into * above

A horizontal line on a speed/time graph means a constant speed.