When asked to provide an estimate of an irrigation system, Pete looked from one end of the field to the other, licked a finger and held it in the air, squinted into the sun and said $$25,000,$ give or take $30\%.$ The technique employed for cost estimation is:

Select one:

a$.$

Ballpark.

b$.$

Parametric.

c$.$

Definitive.

d$.$

Comparative.