At i $=12\%$ interest, F$/$A values at the end of $35,40$ and $45$ years are $431\mathrm{.}6635,767\mathrm{.}0914$ and $1358\mathrm{.}2300$ respectively. At i$=15\%$ interest, F$/$A values at the end of $35,40,$ and $45$ years are $881\mathrm{.}1702,1779\mathrm{.}0904,$ and $3585\mathrm{.}1286,$ respectively. Using the given values, determine the value of i corresponding to F$/$A $=1500,$ and time period of $42$ years.