Answer:
The size of Harry's loan is $9000.
Step-by-step explanation:
D(t) models Harry's remaining debt, in dollars, as a function of time t, in months that is given by :

We can see 200 is in negative that means it is getting deducted from the function. So, Harry must be paying this each month against his loan.
Lets put t = 0, that shows no payments have been made.
This will get the amount of loan, before any payments.

So,
Hence, the size of Harry's loan is $9000.