Maggie's Farm also sells fresh eggs by the dozen. Each week, they can sell up to 10 dozen at the farmer's market, for $5 a dozen. Any remaining dozens are then sold to a local store for $3 a dozen. The farm can produce up to 25 dozen eggs per week. Let M(d) be the amount of money, in dollars, that Maggie's farm makes from eggs during a week when they have d dozens of eggs to sell.

1. From the description above, write down a piecewise formula for M(d), and draw a graph of y = M(d) for d for all d in the domain.
2. Explain how you can tell that M(d) is invertible. Then find a formula for its inverted = M1 (y). Hint: the inverse will also be piecewise, but think carefully about the intervals over which each part of the formula applies.