In a certain packing company, they incentivize their workers according to the number of units packed in the following way: basic salary per day $8.50 and an incentive of $0.45 for each additional unit from 42 units up to 60 units and for those who pack more than 60 units they incentivize it with $1 per additional packaged unit.
a) Build a function that models the total salary received by a worker who packed between 42 and 60 units.
b) Build a function that models the total salary received by a worker who packed more than 60 units