Instrument readings in code

You will write four small functions that work out a reading of the vernier calipers or the screw gauge. They follow the rules of the lesson.

The idea. A vernier has a least count of one main scale division divided by the number of vernier divisions. A screw gauge has a least count of the pitch divided by the number of circular divisions. Every reading is corrected by taking away the zero error.

Your tasks.

1. In vernier_least_count, return the least count for a main scale division msd and n vernier divisions.
2. In vernier_reading, return the corrected reading: the main scale reading plus the vernier division times the least count, minus the zero error.
3. In zero_error, return the zero error of a screw gauge in the units of the pitch. The closed reading closed is on a circular scale of divisions. A reading in the lower half is positive. A reading in the upper half is negative, $-(N - c)$ times the least count.
4. In screw_reading, return the corrected reading: psr plus csr times the least count, minus the zero error.