First Figure Takes 5 Matchstick Squares Build Second Takes 13 Build And Third Takes 21

The first figure takes 5 matchstick squares to build, the second takes 13 to build and the third takes 21 to build a) How many matchstick squares will it take to build the 11th figure? b) How many matchstick squares will it take to build the nth figure? c) How many matchsticks will it take to build the nth figure?