Can someone help please ?!

Aflute is on sale for 20% off. including the discount and 8% tax, the sales price is $216.

What is the gcf of 20c^3-5c^4+30c^6

Will mark the brainliest. paula makes stained-glass windows and sells them to boutique stores. if her costs total $12,000 per year plus $4 per window for the frame. how many windows must she produce to earn a profit of at least $48,000 in one year if she sells the windows for $28 each?