Reaction kinetics- first order reaction rates?

First order reaction of N2O4 to form 2 mol of NO2 has rate constant k=0.023 min-1. How long will it take the initial concentration of N2O4 to decrease to 10% of the original value?
a)600s, b) 100 min c)43.5s d)43.5 min e) 435 min

How to do this question?
THANKs
Update: COuld you explain what formula you are using or just explain a bit more. THANKS.
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