By Jennifer Piacenti Betting analysis of the AL-leading Yankees acquiring one of the best arms on the market in Oakland’s Frankie Montas. In one of the biggest moves before the trade deadline, the AL-leading Yankees (70-34) acquired righty starter Frankie Montas and righty reliever Lou Trivino from the A’s. And the rich get richer. Bet on MLB at SI Sportsbook With Luis Severino landing on the 60-day IL, the Yankees are bolstering a starting rotation which already boasts Gerrit Cole and Nestor Cortes. Yankees starters have the third-best ERA in the league at 3.37, behind only the Astros and Dod…