Let assume that the reserve ratio is 15% and there is an additional reserve of $400. how much extra money supply can be created as a result?

$2666.67

Explanation:

Extra money supply  = 400*(1/15%)

                             = 400 * 6.6667

                             = $2666.67

you will have $2593.74 in 10 years if you set aside $1,000 at 10%

you will have $9321.91 in 20 years if you set aside $2000 at 8%

you will have $1469.32 in 5 years if you set aside $1000 at 8%

you will have $1296.87 in 10 years if you set aside $500 at 10%

you will have $239.66 in 15 years if you set aside $100 at 6%

you will have $4660.96 in 20 years if you set aside $1000 at 8%

the third answer is correct.