The domain of the following relation r {(3, −2), (1, 2), (−1, −4), (−1, 2)} is a: {-1, 1, 3} b: {-1, -1, 1, 3} c: {-4, -2, 2, 2} d: {-4, -2, 2}

The domain is {3, 1, -1}.  Because -1 shows up twice, this relation is NOT a function.

The domain is the set of all unique input values, which here is {3, 1, -1}.

The discount is 8.70 . you dont tell us the percent of tax added so there is no way to find out, unless i'm not seeing anything. without tax its 37.70