3- if you invested money into an account that pays 9% a compounded weekly, how many years would it take for your deposit to double?

9- The function S(d)= 86log d +112 relates the speed of wind, S, in miles per hour, near the centre of a tornado to the distance the tornado travels, d, in miles. Estimate the rate at which the speed of the wind at the centre of the tornado is changing the moment it has traveled its 50th mile.