CREATE TABLE table_77364 ("Province" TEXT, "Membership" FLOAT, "Population" FLOAT, "% LDS" TEXT, "Branches" FLOAT, "Total Congregations" FLOAT)

What's the sum of population when the membership is 51,439 for fewer than 40 branches?
SELECT SUM("Population") FROM table_77364 WHERE "Membership" = '51,439' AND "Branches" < '40'
SELECT SUM("Population") FROM "table_77364" WHERE "Branches" < '40' AND "Membership" = '51,439'