Financial ratio question - Interpretation 1

1. Current Ratio: How does the quick ratio differ from the current ratio?
2. Days in inventory [inventory age] : what is relationship between Inventory age [ inventory / ( Annual COGS/365)] and the Liquidity condition
3. Inventory Turnover [COGS/inventory]: given its relation to inventory age, why use COGS instead of Sales?
4. Day In Receivables [average collection Period ] = A/Rs / (annual Credit Sales /365)
   1. Why only credit sales are included in calculating this ratio?
   2. How does this ratio speak to the liquidity condition?
5. Account receivable turnover [Annual Credit Sales / {A/R} ]: This larger ratio, the better is the firms liquidity condition?