Reasonable definitions of the decision variables are: a) x subscript 11 household without children under 16 and without premium subscription
x subscript 12 household without children under 16 but with premium subscription
x subscript 21 household with children under 16 but without premium subscription
x subscript 22 household with children under 16 and with premium subscription
b) x subscript 11 number of interviewed households without children under 16 and without premium subscription
x subscript 12 number of interviewed households without children under 16 but with premium subscription
x subscript 21 number of interviewed households with children under 16 but without premium subscription
x subscript 22 number of interviewed households with children under 16 and with premium subscription
c) x subscript 11 cost of interviewing a household without children under 16 and without premium subscription
x subscript 12 cost of interviewing a household without children under 16 but with premium subscription
x subscript 21 cost of interviewing a household with children under 16 but without premium subscription
x subscript 22 cost of interviewing a household with children under 16 and with premium subscription
d) All of the above are reasonable definitions.
e) None of the above.