Final answer:
You can use the COUNTA function to count the number of non-blank cells in the 'billable' column (D2:D13) and enter the formula in cell D14.
Step-by-step explanation:
To count the number of non-blank cells in the 'billable' column (specifically, cells D2:D13) and enter the formula in cell D14, you can use the COUNTA function in spreadsheet software. The COUNTA function counts the number of cells in a specified range that are not empty or blank.
To use the COUNTA function, enter the following formula in cell D14:
=COUNTA(D2:D13)
This formula will count the number of non-blank cells in the 'billable' column and display the result in cell D14.