I think I am correct and the answer in the book is wrong but i figure a second opinion wouldn't hurt.

Question

Fgt's home income tax business operates only during tax season. Last year Fgt grossed $28,350 INCLUDING GST (5% in this case). During that season she spent $8000 BEFORE GST on her pper and other shit. How much does Fgt owe the CRA for GST?

So this is what I did.

28,350/1.05 = 27,000 Which means fgt already gave them 1350 for the GST

8000 x 1.05 = 8400... 400 of which is tax that she owes

1350 - 400 = 950 so she should be given back 950 for overpaying?

wut

Fgt should just launder drug money through the business so she can hire MNP.

Well, did she already pay the 1350 GST to the CRA for last year? I read this as "Fgt is doing her taxes for last year and needs to figure out how much to pay CRA." In other words, she hasn't paid any GST for last year yet.
So yeah, she made 27,000 and 1350 in GST. Her business expenses were 8,000, which are tax-deductible. So she owes them GST on 19,000, which is 950.

Is the disagreement with the book purely on whether she owes them 950 or they owe her? Or is there an actual number difference?