In the following table we present prices for three commonly used sources of energy-motor gasoline, natural gas, and electricity-for the years 1990 through 1996:

a. Consider a family that consumes 1,850 gallons of gasoline, 150 mcf of natural gas, and 17.000 kilowatt-hours of electricity every year. Construct the Laspeyres index for these energy products using 1990 as the base year. Then describe how energy prices have changed for this family over this period.
b. Consider a family having the following energy consumption pattern from 1990 to 1996:

1990 1991 1992 1993 1994 1995 1996 Motor Gasoline Price (S per Gal.) 1.22 1.20 $.9 1.17 $1.17 $1.21 1.29 Year Natural Gas Price (S per mcf) Electricity (S per Kilowatt-Hr.) $066 .067 $.068 .069 $069 $.069 $.069 $1.71 1.64 $1.74 $2.04 $1.85 $1.55 $2.25 Year Motor Gasoline (Gallons) 2,200 2,100 2,000 950 1,950 1,900 1750 Natural Gas (mcf) Electricity (Kilowatt-Hr) 15,000 16,000 17,000 18,000 20,000 21,000 22,500 1990 1991 1992 1993 1994 1995 1996 150 150 150 150 150 150 150