The amount of money they have is enough for $99 spending. The answer can be found by testing two numbers and seeing whether the amounts need to be increased or decreased to make the distance between them 17, with a sum of 99.
40 and 57: distance of 17, but not enough for $99. $41 and $58 equal 99, with a distance of 17 between them. Jenny, with $17 more, has 58. Susan has 41.
