Tier 2 employer sponsored - refused - salary vs weekly hours

I have received a letter from Home office which they refused my tier 2 work visa application. The reason stating that the salary is inappropriate. The minimum salary requirement for my job is £21600 which home office based on 39 working hours weekly. However, my company COS wrongly stated that £21600 and working 40 hours a week. Therefore, my tier 2 visa application has been refused. My company is appreciated to increase to the appropriate level we didn't aware that the minimum requirement based on 39 hours weekly instead of 40 hours weekly basis.

My student visa has been expired on 16/1/2017. I got the refuse decision on 23/1/2017. They allow me to apply administration review within 14 days, but is there any chance to success or the chance is low ? Can I apply review to extend my staying and at the meantime to reapply for the visa? How can I deal with this situation? I am so desperate:( a lot thanks!!