$(5$ pts$)4.$ A smal speaker emits sound waves uniformly in al directions. Point P is $20\mathrm{.}0$ m from the

speaker. By what multiplicative factor must the power output of the speaker be increased in order to

increase the sound intensity level at point P by $20$ dB$?$

$($a$)10$

$($b$)20$

$(($c$)100$

d $)200$

$($e$)400$

$($f$)$ none of the above answers