How does the coupon deal work for free mug if you pay 1.89 coffee how much is tax for the first visit to get your free cup and coffee1

I've used many of Sprinfield Dunkin. With tax refill is $2.02

The first cup is free then 202 after for a refill

If you can find the mugs now it's dollar 89 for the coffee with the tax but all dunkin' donuts don't under the refills I found that out when I bought a mug Palmer Ware Granby cover it Springfield does not at least four of them that I've tried