The PW$-$based relation for the incremental cash flow series to find $\backslash$Delta i$^*$ between the lower first$-$cost alternative X and alternative Y has been developed.

$0=-30,000+9000($P $/$ A$,\backslash$Delta i$^*,10)+(-4000($P $/$ F$,\backslash$Delta i$^*,10))$

Determine the highest MARR value for which Y is preferred over X$.$ Any MARR value less than $\%$ favors Y$.$