please answer all 3

Investing. How many years will it take $1,000 to grow to $1,600 if it is invested at 6%(A) compounded quarterly? (B) compounded continuously? (A) years (Round to two decimal places.) (B) years (Round to two decimal places.) An investor bought stock for $40,000. Fifteen years later, the stock was sold for $60,000. If interest is compounded continuously, what annual nominal rate of interest did the original $40,000 investment earn? The annual nominal rate of interest earned is % (Round to two decimal places as needed.) A mathematical model for the decay of radioactive substances is given by Q=Q0ert where Q0= amount of the substance at time t=0,r= continuous compound rate of decay, t= time in years, and Q= amount of the substance at time t. An isotope has a half-life of 20 years. What is the continuous compound rate of decay? The continuous compound rate of decay is r= (Type an integer or decimal rounded to four decimal places as needed.)