Step by step explanations please, any graphs , formulas , definitions

Q2. Which (if any) of the following functions represent constant elasticity of demand (CED) curves? (Consider only the range where quantity demanded Q, and price P are positive.) i. QD = 10 ii . QD = 10 P+1 iii QD = 10 In (P +1) iV . QD = 10 - PQ2. Which (if any) of the following functions represent constant elasticity of demand (CED) curves? (Consider only the range where quantity demanded Q, and price P are positive.) i. QD = 10 ii . QD = 10 P+1 iii QD = 10 In (P +1) iV . QD = 10 - PQ3. Consider the following two series: Years from now 1 2 3 4 Series A f100 f100 f100 f100 Series B E0 $500 Which series has the larger present discounted value if the interest rate is... ...0% per year? ii . ...5% per year? iii. ...50% per year? iv. ...500% per year