yes, but i'm an accountant

some days, keeping my patience at work is extremely challenging. . . i had an annoying exchange with a customer that if i weren't involved, i would laugh. . .

c: excuse me, can you help me?

v: sure, how can i assist you?

c: i want to exchange this item i purchased on my registry. some of the crystals fell off.

v: ok, let me see if we have that item in stock.

i check the register and go back to the stockroom, lo and behold, we actually do have the merchandise and i happily bring it to the customer. after i start processing the exchange she stops me.

c: actually, i think i want to get these two items instead. . .

v: ok, let me check to see if we have them.

i bring out the boxes and first return the item c brought in and rang her up for the two new items.

c: wait, i didn't get my tax back?

v: i'm sorry, what's that?

c: you didn't give me my tax back. c brings out her cell phone and does some fuzzy math on her calculator.

c's mom: (in a smug tone) she is an ccountant. she will know.

wtf? all of this is automatically calculated.

v: i don't understand what you mean. everything is calculated pre-tax and that tax is added at the end so it all cancels out.

getting tired of the accountant's unconvincing explanation of how she was cheated out of tax, i pull out my calculator and re-calculate everything for her.

v: now, whether we tax before taking the difference or after doesn't matter.

let's say:
A= pre-tax amount you are due from the return
B= pre-tax amount you owe the store for the two items you are purchasing
so, C= A-B is the pre-tax amount you owe the store then C'=C * NY tax is the amount you owe the store including tax

now, let's say:

A'=A* NY tax is the amount you are due from the return including tax
B'=B* NY tax is what you owe for the two items including tax
then C'=(A* NY tax) - (B*NY tax)= (A-B) * NY tax= C * NY tax

so C' the net amount you owe including tax remains the same whether you tax the return and purchase amounts before you take the difference or after you take the difference.

c: ahhhh, i see. you're right.

damn right i'm right. after all. . i do have a masters in economics. but i would never say that out loud because that's obnoxious.