Please help me with this question :)​

Answer this question, only if you know the answer. 30 points and brainliest!

The median of a data set is the measure of center that is found by adding the data values and dividing the total by the number of data values that is the value that occurs with the greatest frequency that is the value midway between the maximum and minimum values in the original data set that is the middle value when the original data values are arranged in order of increasing (or decreasing) magnitude

What is the gcf of 20c^3-5c^4+30c^6