What questions should I ask the supplier when they are proposing a quote?

What questions should I ask the supplier when they are proposing a quote?

These are trademarks of any reputable company, including solar installers:
High-Quality Materials – Ask them what products and brands they offer, and why. Established businesses will give you evidence-based reasons for offering specific solar products.
Informative, Transparent Sales Process
No Pressure Tactics — You should never feel rushed towards a decision
Quick, Attentive, and Courteous Communication (Both on phone and in person)
Timeliness in keeping appointments
Post-Installation Service
Numerous Positive Online Reviews