A lot of my answers are wrong. I'm not sure why. Please show work so I can double check what I did wrong.

Answer the following time value of money questions assuming the interest rate is 12 percent. a. What is the present value of $2,100 to be received in four years? b. What is the present value of $2,100 to be received in eight years? c. What will be the value in seven years of $12,600 invested today? d. How much would you pay for the right to receive $5,600 at the end of year 1,$4,600 at the end of year 2 , and $8,600 at the end of year 5 ? e. How long will it take for a $2,600 investment to double in value? f. What will be the value in 20 years of $2,400 invested at the end of each year for the next 20 years? Note: Round your answers to 2 decimal places