A computer can execute 36 instructions per microsecond. How many instructions can it execute in 4 minutes?

I have no clue how to do this one, because I don't know how much is a microsecond. I need help please! Thanks!

36 x instructions over micro. sec x 1,000,000 x micro. sec over sec. x 60 x sec. over min. x 4 min.'s over 1 = 8,640,000,000

How would you do this problem?

30% of the Beads in a jar are red. The rest are blue. If here are 500 more blue beads thatn red, how many beads are there altogether?