CREATE TABLE table_29289372_1 (population__2010_ VARCHAR(255), income_classification VARCHAR(255), city_municipality VARCHAR(255))
When itogon, benguet is the city/municipality and 1st class is the income classification how many measurements of population in 2010?
    
SQL: SELECT COUNT(population__2010_) FROM table_29289372_1 WHERE income_classification = "1st Class" AND city_municipality = "Itogon, Benguet"