Compute the future value of a $$200$ cash flow for the following combinations of rates and times.

Note: Do not round intermediate calculations. Round your answers to $2$ decimal places.

a$.r=8\%$;$t=10$ years

b$.r=8\%$;$t=20$ years

c$.r=4\%$;$t=10$ years

d$.r=4\%$;$t=20$ years