In the table says that every letter that weighs less that 1 oz. have a price of 42, in the graphic we represented that in this part:
Following the data in the table as above we got the final graphic.
And for the question:
If you have a letter that weighs 1.7 oz. it will be more than 1 oz. but less than 2 oz. so you will pay 66, as we can see in the following graphic:
