using an if statement to compare 2 columns of data and return text information

Hi

This may seem like a really simple but I am having a problem achieving the required result.

I have 2 columns of data reflecting English and Maths Grades. If the grade for either English or Maths is a C- or below then they haven't achieved the required result in these two subjects so the the third column will indicate which subject they did not achieve in (English, Maths or Both). If the student achieved a C or above in both English and Maths my formula should return a blank cell.

Please have a look at the attached spreadsheet as it will make more sense - I require a formula in the the third column please.

I look forward to hearing from you

kind regards
Vanessa