CREATE TABLE table_20067 ("Name" TEXT, "Year" FLOAT, "Landfall" TEXT, "NHC Advisory Number" TEXT, "V ( mph ) " FLOAT, "R ( miles ) " FLOAT, "Saffir-Simpson Category" FLOAT, "CHI" TEXT)

What is the CHI (Carvill Hurricane Index) when the NHC advisory number is equal to 49b?
SELECT "CHI" FROM table_20067 WHERE "NHC Advisory Number" = '49B'
SELECT "CHI" FROM "table_20067" WHERE "NHC Advisory Number" = '49B'