Calculating Demand confidence

I recently was asked to work on a business problem related to sales using Data Science. This required me to come up with a Demand confidence number that would specify how confident we are on delivering goods to customers given a certain supply on a particular day. This demand confidence is dependent on factors like quotes, agreements, profitability.

how to model this kind of problem to come up with weightages to above said factors and calculate a confidence number?

the current process is to depend on experience of sales persons and perform manually.

How should I start? Please help me with suggestions