I have four boxes, each containing a number of red marbles and blue marbles.

Box A | Box B | Box C | Box D | |

$\text{Red marbles}$ | $70$ | $y$ | $2$ | $7$ |

$\text{Blue marbles}$ | $30$ | $3$ | $98$ | $53$ |

If the probability of randomly selecting a red marble from Box A is $a$, and the probability of randomly selecting a red marble from Box B is $b$, then $a < b$.

Suppose we group all the marbles in Box A and Box C into another Box AC; likewise we group all the the marbles in Box B and Box D into another Box BD. Now, there is a higher probability of randomly selecting a red marble from Box AC than from Box BD.

What is the sum of the smallest and the largest possible values of $y$ for which the above criteria is satisfied?