chemistry question :reaction kinetics

Feb 2016
So i just get homework from my big sister lol. Homework??are you still at school? Ofc not. Just talking to myself lol. So, the question is difficult and she asked for me to help her solved it. So the question is
A + B -> products
the rate equation for the above reaction is :
Rate = k [A]
with an initial concentration of 1.0 mol dm^-3 of A and 1.0 mol dm^-3 of B, the reaction is 20% completed in 20 minutes. Calculate (a) the rate constant, and (b) the time taken for the reaction to be 60% completed.
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