Extract (only non blank cell + highest value) data from multiple tabs

Hi guys...Please help me with my workbook (attached)

In the workbook there are four tabs i.e. Cumulative, Data1, Data2, Data3. Tabs Data1, Data2, and Data3 contain information of student performance in each semester.

My question is: how to extract automatically informations from Data1, Data2, and Data3 and put it all on Cumulative with these two additional conditions:

• I only want to extract all non BLANK cell of B5:C9 from each Data1, Data2, and Data3
• If there are subject that retaken, I want to extract data with the highest grade. (as you can see in Data1, Data2, and Data3 there is one subject that always appeared i.e. BIO1201, this subject was retaken twice with highest grade is B).

I am sorry for my bad english, i hope you can understand my question. Thank you so much!