Solve for the unknown interest rate in each of the following:

Note: Do not round intermediate calculations and enter your answers as a percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.$

$\backslash$table$[[,$alue,Years,Interest Rate,Future Value$],[$$$,780,7,0,1,511],[,970,8,0,1,848],[,21,500,19,5,148,332],[,76,800,22,$c$,325,815]]$