Answer:
Big buy must sell at large at a smaller price which will give tough time to Radio Shack and this is the threat that RadioShack don't want to bear.
Step-by-step explanation:
Best Buy will choose large quantity because it helps in satisfying the needs of public at large at a lower price. This will force RadioShack to lower its price which will result in losses and this fear of losses will act as a enterance deterent. Though the profit on this strategy is lower but it will safeguard future revenues as RadioShack will not enter the market or get defeated very quickly.