Suppose strontium-90 decays at a rate of 2 percent per year, math homework help

1. Suppose strontium-90 decays at a rate of 2 percent per year.

(a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) 
Answer: P(t)=

(b) Estimate the half-life of strontium. 
Answer: 

 
(c) If presently there is 4 grams of strontium, estimate how many grams of the substance will remain after 50 years. 

2. Your business associate who owes you $9000 offers to pay you either $7110 now or else to pay you 6 yearly installments of $1500, the first installment paid now. Assume a 6.2% market interest rate, compounded continuously. 

How much would you have at the end of 6 years if you choose to take the $ 7110 offer now, and you use the market to earn interest on the funds? $ 

How much would you have at the end of 6 years if you choose to take the installments each year, and you still used the market to earn interest on the the funds? $ 

Is it better to take the lump sum? 

(Y for yes, N for no.)