Shell script used to increase/decrease memory on my server

UpgradeMEM

#!/bin/bash

# This cronjob runs at least once a minute and will check if the usage of RAM is more than 75%
# if it is more than 75% it sends me an e-mail and invokes the API. API call removed from the example.
# When the percentage left after a possible decrease is 70& then it decreases the RAM to that level

TOTAL=`free | grep Mem: | awk '{print $2}'`
USED=`free | grep Mem: | awk '{print $3}'`

INCREASE=$(((TOTAL/1024)+512));
DECREASE=$(((TOTAL/1024)-512));
PERCENTAGE=$(((USED*100)/TOTAL));
PERCENTAGE_DECREASE=$(((USED*100)/(DECREASE*1024)));

if [ $PERCENTAGE -gt 75 ]; then
        if [ $INCREASE -lt 10000 ]; then
                # Send e-mail about increasing memory
  		# Invoke API to increase memory
        fi;
elif [ $PERCENTAGE_DECREASE -lt 70 ]; then
        if [ $DECREASE -gt 768 ]; then
                # Send e-mail about decreasing memory
		# Invoke API to decrease memory
        fi
fi;