$299 and $199 adds up to 498, including the tax rate 7.5% and your total is $535.35
This is equal to the probability that no light fail. Probability of one light not failing = 0.98.
P(no light fails) = 0.98^20 = 0.67 or 67% to nearest percent.
No it does not. If q=b and b=t then q=t is the correct answer.
John's effective annual rate is about
(1 +.0576/4)^4 -1 ≈ 5.8856%
According to the "rule of 72", John's money will have doubled in
72/5.8856 = 12.23 years
John's balance will be $4500 in 1989.
_____
Since you're only concerned with the year (not the month), you don't actually need to determine the effective annual rate. The given rate of 5.76% will tell you 72/5.76 = 12.5 years. The actual doubling time is closer to 12.12 years, so using the effective rate gives results that are closer, but "good enough" is good enough in this case.
