Need some help with this question, answering a, b, c, d. Thanks!!

According to the short NYTimes article "Fairness on Sales Taxes" there is an inequity surrounding the online collection of sales taxes, leveling the playing field among competing firms, the progressive or regressive nature of sales tax (using the average tax (total tax/total income) approach, shifting the burden of sales tax (who pays determined by changes in producer/consumer surpluses). Using the content of that article in the NY Times discuss:

a.) What is meant by "fairness" with regard to taxes, anyway? Discuss tax burdens (who pays the tax) and fairness informed by elasticity of demand and elasticity of supply along with expected size of dead weight loss (DWL) under different combinations of elasticity of demand and elasticity of supply scenarios. b.)And, explain why it is important to maintain tax fairness/tax efficiency in our society between online and bricks-and-mortar retail sellers c.) Explain reason(s)sales taxis basically equitable or not equitable.Note: For part c.) please use a hypothetical example of average taxes paid by a consumer/tax payer named Jenny who lives in San Francisco, earns $30,000 income per year, pays a 10% sales tax rate oneverythingshe purchases (rent, food, entertainment, transportation, etc.), spends all $30,000 income (not hard to do in S.F. on her income) so she effectively pays $3,000 taxes on $30,000 income. Calculate her average tax rate. Then, compare and contrast her average tax rate (equity-wise) with a consumer/tax payer named Julio who also lives in San Francisco, earns $100,000 income per year, pays a 10% sales tax rate oneverythinghe purchases (rent, food, entertainment, transportation, etc.), and spends identically to Jenny i.e. $30,000 of his income (saves $70,000) so he effectively pay $3,000 taxes on $100,000 income. Calculate his average tax rate.d.)What makes sales tax an example of a regressive, progressive, or flat tax?