4. Bucket A contains 4 kg of liquid fertilizer with a concentration of $20 \%$, Bucket B contains 141 kg of liquid fertilizer with a concentration of $50 \%$, and Bucket C contains 5 kg of liquid fertilizer with a concentration of $x \%$. After mixing them, the resulting liquid fertilizer has a concentration of $(x+5) \%$. What is $x=$ $\qquad$
$44$