How do i tell Excel to count different text entries in a column?

Dear experts,

Here is something that is taking up a lot of my team's time. We have to count the times of a Category, and insert that value in a column called "Mentions", here is the scenario:

excel.jpg

Column A - Specific ID's
Column C - Brands
Column D - Category
and Column N - Something we need to manually calculate

Many ID's (Column A) have multiple brands and categories (column C and D) - but these are ultimately tied to one ID.

How the "Mentions" Column came about was, we needed to insert the total for a specific ID that has multiple brands / categories.

In the image above, the ID "X00069906597" has 1 brand ("Apple"), but 2 categories ("Corporate", and "Mobile/ Tablet"), so what we needed to do is to insert "2" in the "Mentions" column.

Is there a faster way to do this? A million thanks!

Jocelyn