The rate constant of the reaction $A \to B$ is $0.6 \times 10^{-3} $mole per second. If the concentration of A is 5 M, then cencentration of B after 20 minutes is -

Question

( A ) 0.72 M
( B ) 1.08 M
( C ) 3.60 M
( D ) 0.36 M