Suppose 6 quarts of a solution that is 45% antifreeze is mixed with 2 quarts of a solution that is 19% antifreeze.

6+2=8 quarts of a new solution

0.45*6  - quarts  antifreeze in a solution that is 45% antifreeze
0.19*2  - quarts  antifreeze in a solution that is 19% antifreeze

x- concentration of a new solution
8x -  quarts  antifreeze in a new solution 

0.45*6 + 0.19*2 = 8x
3.08=8x
x= 0.385 =38.5 %

Reaction involved in present system is :   c12h22o11 + h2o → 2 c6h12o6the reaction system is obeying following rate law:   rate = k[c12h22o11]thus, it is a first order reaction.now, for 1st order reactionrate constant (k) =  given: initial conc. = 3.0 g, final conc. = 2.7 g, t = 2.5 h∴rate constant (k) =  ∴ k = 0.04215 h-1now, for 1st order reaction, half life = 0.693/k = 0.693/0.04215 = 16.4 hthus correct answer is option b