How many different rays can be formed from five collinear points?

The solution in each item is enumerated below:

For item#1,
Interest in a year = savings amount * interest rate * time
Interest in a year = $55,000 * 2% * 1 year
Interest in a year = $1,100

For item#2,
Amount to keep inflation = $55,000 * 3.24% * 1 year
Amount to keep inflation = $ 1,782

For item#3,
Buying power loss = $1,782 - $1,100
Buying power loss = $682