CREATE TABLE table_19705 ("Prefix size" TEXT, "Network mask" TEXT, "Available subnets" FLOAT, "Usable hosts per subnet" FLOAT, "Total usable hosts" FLOAT)

When the network mask is 255.255.255.128 what is the lowest available subnet?
SELECT MIN("Available subnets") FROM table_19705 WHERE "Network mask" = '255.255.255.128'
SELECT MIN("Available subnets") FROM "table_19705" WHERE "Network mask" = '255.255.255.128'