Answer:
The annual increase was approximately $0.002
Step-by-step explanation:
In order to know the annual compound increase in the cost of the first-class postage during the 54 year period, we need to know the rate at which the compound interest was calculated. We can know that using the following compound interest formula:

P = principal amount (the initial amount for the envelope)
r = annual rate of increase
t = number of years the amount is increased.
A = amount of money accumulated after n years, including the increase.
Now, we have our Amount at the 54th year to be 0.45dollars, when the principal is 0.04dollars.
Therefore, we have
A = $0.45
P = $0.04
r = unknown (that's what we are looking for)
t = 54
Substituting these into the formula, we have:

Dividing both sides by 0.04 we have:

Taking the 54th root of both sides we have(approximately):

The above gives:

This gives:

Therefore, the money increased annually at the rate of 5% approximately, and that would be

Which is $0.002 approximately.