Power Query - True or False based on data in rows (whilst ignoring "null" values)

Hi there,

I'm trying to ascertain the number of pupils that have achieved all their grades being 7 to 9. 

For this, I want power query to look across all subjects, check if the value is 7 or greater, and if so for all subjects, return a value of "true" in a final column. 

However, not all pupils take the same subjects, and a lot of the cells will have a null value - but I don't want these null values to be considered when ascertaining if they achieved all grades 7 to 9. I want the null values ignored.

E.g.

Any help would be greatly appreciated. Thanks so much.