In the script below, for a student's exam marks, what can be used to remove all $-99$ from exam$\_$marks and extract the correct marks?

import numpy as np

exam$\_$marks $=$ np$.$array$([[89,78,92,90],$

$[-99,-99,-99,-99],$

$[80,90,78,92],$

$[-99,-99,-99,-99]])$