The ELISA plate

A dictionary holds the readings of the wells of an ELISA plate. You will decide which samples are positive and work out the share that is positive.

The idea. A sample is positive when its reading is above the cutoff. A reading equal to the cutoff is not positive.

Your tasks.

1. Finish result. It gives "positive" or "negative" for one reading.
2. Finish positives. It gives the sorted list of the names of the positive samples.
3. Finish percent_positive. It gives the per cent of the samples that are positive.