More than 3 but less than or equal to 4 days is the average processing time per income tax form.
Option - a
Explanation:

So, T = 3.2Days
The average processing time per income tax form is more than 3 but less than or equal to 4 days.
Work in process relates to a partially completed portion of the stock of a business. The valuation of a partially finished stock is also sometimes referred to as the balance sheet products in operation, particularly when the company produces tangible goods instead of services.