$9\mathrm{.}34$o An airplane propeller is $2\mathrm{.}08$ m in length $($from tip to tip$)$

with mass $117$ kg and is rotating at $2400$ rpm $($rev$/$min$)$ about an

axis through its center. You can model the propeller as a slender

rod. $($a$)$ What is its rotational kinetic energy? $($b$)$ Suppose that, due

to weight constraints, you had to reduce the propeller's mass to

$75\mathrm{.}0\%$ of its original mass, but you still needed to keep the same

size and kinetic energy. What would its angular speed have to be$,$

in rpm$?$